Tech on a plane

First of all, there's no limit as to the number of electronic devices you can bring on a plane. It's just a matter of size and weight of your carry on and personal item. Whatever fits.

Second, most people would strongly recommend against packing electronics in checked luggage, where it would be at risk for damage, theft or loss. Not to mention the risk of fire from lithium batteries.

Of course you need to bring the chargers for your devices. And an adapter so that the charger will fit into European electrical sockets. You may find that your planes, trains and hotel rooms also have USB or USBC sockets as well. And finally, if you don't think your phone battery will last a full day between charges, get a portable power bank.

I would advocate to carry the laptop (actually, all electronic devices) in your carry-on
bag on the plane.

a) less chance for theft
b) small but non-zero chance for issue with laptop batteries and in the hold you
won't see it
c) you can use the laptop on the flight if you want to

If you want more storage without having to upgrade, most likely the easiest
solution is to buy a card reader that connects to the lightning port on the phone,
and then an SDHC card.

Unless you are having major issues carrying it, the airline is not usually going to
make a big deal about the weight of your carry-on bag. And if you can't get
a laptop, tablet, and other assorted items into a backpack, you're not trying.

I am not aware of a TSA limit on the # of devices, but it's true that between
the devices, cables, etc, it can be a lot of stuff, so it pays to have a packing
method figured out ahead of time.

I carry a laptop with me every time I travel. I would never put it in checked luggage for the reasons stated above with theft at the top of the list.

I won't be able to store much video

Store your video in the cloud. If you aren't comfortable with that, there are external storage devices that can connect to an iPhone or iPad.

the batteries will run down

There are external battery devices

You’re supposed to bring any item with a lithium battery in it in your carry-on.

You are free to do as you wish.....but.....never, ever,ever, ever, ever, ever put anything of value in your checked luggage especially jewelry and electronics. It should always be with you.

Anyway, you shouldn't put any electronics with lithium batteries in checked luggage. Fire hazard.

Note in particular what the last two posts said. It is not only “you should not” but actually “you must not” put devices with lithium batteries, especially fully charged ones or large one, in checked baggage. Most airlines list this requirement on the check-in page and you are supposed to agree and comply.

We are even careful not to pack our electronic deceives in a carry-on bag, in case they require it to be gate-checked because the bins are full. All electronics and batteries/power banks go in the “personal item” that goes under the seat.

You probably did not hear of this if you live outside California’s Bay Area region, Area, but 2 days ago there was a fire on board an American Airlines plane at the gate in SFO, during the boarding process. Smoke, and then flames appeared at the back of the aircraft, and the plane was quickly evacuated using the emergency exits and chutes. The cause was some kind of electronic device in a backpack. Good thing it did not happen after the plane took off.

Aside from the fire hazard/prohibition already mentioned if I understand correctly you really only want the laptop for "insurance" for photo storage, anyway? Since you will have your IPad that's so much more portable.
If you're only worried about physically moving your daily photos to other than cloud storage, using a compatible device would be a much easier solution and could store in your personal item with your chargers?
https://support.apple.com/guide/iphone/external-storage-devices-iph95baac91f/ios
I have a Pixel phone but love the ease of just creating an album to share with family in real time as I travel. If I need or want do any editing, I wait to add to the album until waiting for a train or from the hotel.

I got a Rick Steves TSA approved lock to lock my checked bag and plan to carry my laptop there.

You cannot put your laptop in a checked bag unless you remove the battery. Aside from that, I would never put anything valuable like a laptop in a checked bag. Put all of your electronic devices in your carry-on. I don’t know what TSA limit you are referring to but a phone, an Ipad, and a laptop would not be an issue.

All devices with lithium batteries must be in your carry on bag due to fire risk. This includes a power bank, which I highly recommend for your phone. Your battery will run down. I love this one: https://a.co/d/7iigAHh

If you are bringing your laptop solely to store your photos, there are lots of other options. You could use cloud storage, or store them on a device like this. No need to lug around a laptop. https://a.co/d/5hSpBF6

When you go through airport security, they usually ask you to remove iPads and laptops from your bag and place them in a separate bin. Another reason to leave the laptop at home.

Here are the TSA rules for lithium batteries on a plane:

Spare (uninstalled) lithium ion and lithium metal batteries, including power banks and cell phone battery charging cases, must be carried in carry-on baggage only.

With airline approval, passengers may also carry up to two spare larger lithium ion batteries (101–160 Wh) or lithium metal batteries (2-8 grams). This size covers the larger after-market extended-life laptop computer batteries and some larger batteries used in professional audio/visual equipment. There is a limit of two spare batteries per person for the larger lithium ion batteries described above (101–160 watt hours per battery. For more information, see the FAA regulations on batteries.

This instruction covers spare lithium metal and spare rechargeable lithium ion batteries for personal electronics such as cameras, cell phones, laptop computers, tablets, watches, calculators, etc. This instruction also includes external battery chargers (portable rechargers and power banks) containing a lithium ion battery. For lithium batteries that are installed in a device (laptop, cell phone, camera, etc.), see FAA regulations for "portable electronic devices, containing batteries."

https://www.tsa.gov/travel/security-screening/whatcanibring/items/lithium-batteries-more-100-watt-hours

This is the FAA regulation for lithium batteries: https://www.faa.gov/hazmat/packsafe/lithium-batteries

By the way, the rule also applies to luggage with the built in battery chargers. You have to take the battery out before you check the bag.

I can't decide which portable devices to bring in my carry-on and could use some advice. I want to bring my iPad mini so I have a screen big enough to do a lot of reading, but I'm nervous that even between that and my iPhone 12 I won't be able to store much video, or that the batteries will run down on both devices on a long day. Am I worrying over nothing? Would taking another electronic device or charger put me over the TSA limit? (it seems a little ambiguous).

Lisa, I'm sure after reading the multiple posts above, you've learned everything there is to know about lithium batteries and where to carry them. :-)

With regards to your other concerns, you can always bring a backup charger for your iPhone. As mentioned above, there are power banks that you can bring along in your bag that will recharge your phone in no time. Personally, I like the Anker power banks. They are sold on Amazon and on their website. You can also find them at Costco Next sometime, if you are a member. Here is a link to one on Amazon that can be used with an iPhone 12. I use mine a lot when traveling, especially when I'm in larger cities and won't be heading back to the hotel during the day. They are invaluable and most of them can charge a phone 2-3x over.

Also, it helps to have a separate pouch or bag for your electronics. I keep mine in a small Tom Bihn travel tray (the plugs) and keep the charging cords in a Tom Bihn cubelet. Some people use designated bags for their tech stuff like this one from Target. Any place that sells travel gear will have them; although really, any decent sized pouch will do.

Once you are in your room, you can log onto wifi and work with your photos, recharge everything you need, and you should be good to go. It shouldn't be any problem to upload them to your online storage. If you are worried about cloud space, Apple gives you an extra 50GB of storage for $.99 a month, or 200GB for $2.99.

Also is the reason you are bringing your laptop just to upload photos? You might want to consider bringing your laptop OR your iPad mini. For one thing, your phone photos should automatically upload to the cloud. Make sure that your settings allow your photos to be optimized to reduce the amount of storage. To find that setting, go to the Settings app, click on Photos, and then make sure that there is a check-mark next to "Optimize iPhone Storage." If not, check that. Unless there is another reason you want both, think about leaving one behind. The laptop will be heavy and will be a pain to pack and bring along.

Whatever you take, you'll need to remove it from any case and put it in a bin to go through airport security. Since one laptop or iPad mini looks much like another, and could be picked up accidentally by someone, mark yours in some way. My laptop has an orange daisy made from colored masking tape strips and my husband's has large googly eyes.

Thank you so much for the tips. I think I’ve got it figured out now.

never, ever,ever, ever, ever, ever put anything of value in your
checked luggage

On a side note: that goes for prescription medicine too. At least keep enough for a week in your personal item.

There are a lot of online backup and storage options, many of them free. I would not lug my laptop on a pleasure trip simply to service photos. Opinion.

"I would not lug my laptop on a pleasure trip simply to service
photos. Opinion."
I sure agree with that. Three better alternatives:
1. Get a little MicroSD jack that plugs into the phone, and copy all photos to it.
2. Using our Samsung phones, use Quickshare (via Bluetooth) to copy my wife's photos to my phone, and vice-versa.
3. Edit photos in the evening at the hotel (which makes them 1/8 the size). Then upload them to a free Google account using wifi. With 15 Gb of free storage, I can store a zillion compressed .jpg photos. When I get home, I can crop & edit them, re-sequence & rename them, on my laptop. This method (#3) might not be the best if you are saving long videos, though.

Not going to suggest anything, but I personally just take the odd pic with my phone, and have them up on Google Photos, shared with family. I can't be bothered with anything else on a trip. Too busy! BUT it is a very good idea to have a small charging brick, because you do end up using the phone (live Google Maps for buses etc, for example), and running batteries down sometimes.

Check out You Tube for information on things to pack and how to pack. One of the ones that I watch is Travel Tips by Laurie. Of course I’ve haven’t been to Europe, yet.

it is a very good idea to have a small charging brick, because you do end up using the phone (live Google Maps for buses etc, for example), and running batteries down sometimes.

This is especially true when traveling by rail, as the trains often traverse rural areas with spotty cell coverage. Cell phones burn their batteries quickly when they're searching for a signal.

Great reminder, phoffen2001!