Driving from Fussen: Hohenschwangau + Neuschwanstein

I just have some things for you to consider:
Since you are fit adults, It's less than a 30 minute walk from the parking up to Hohenschwangu, but OK budget 30 minutes. If your tour is at 9:55, there's no need to be earlier than 9:30 am. If you are there earlier, all you will do is wait outside. So you can arrive by 8:30 am, park and walk the up to Honhenschwangu and still be at the entrance by 9:15, assuming you have your tickets and you don't need to wait in line at the ticket office.
OK, walk down from Hohenschwangu (budget 20 minutes) puts you back near parking, restaurants, visitor center at 11:00 am

When are you going to eat lunch? And how long will that take? The restaurants are not quick. Bathroom breaks?

If you take the shuttle up to Neuschwanstein, the bus drops you off above the castle and the path to Marienbruke is right there.
Then you walk down- 10-15 minutes to the Castle waiting area and entrance. You will stop often to take pictures on the walk down.
If you tour is at 1:55 pm, there is no need to be there earlier than 15-20 minutes. If you arrive earlier, you will be standing outside the castle entrance. about 15 minutes before your timed entrance, you will be let into the courtyard to wait. Then the electronic gates with a timer will let those people in with 1:55 tickets in at 1:55 exactly. You will enter, find your guide and take the tour.
The tour may take 45 minutes, but there are the views from the balconies you will visit on your own and take pictures and there are some exhibits and areas to venture on your own, so I would budget 1 hour.
Then, according to your plan, you want to walk back UP the steep hill (15-25 minutes) to the path to Marienbrucke. OK, 30-45 minutes for that.
Then an hour to walk back down or take the shuttle back down. (You can buy one-way shuttle tickets, if you are intent on walking down.
Be sure to include, bathroom breaks, a stop at the gift shop and time to take pictures.

I might suggest, that you adjust your timing, so you take the shuttle up to N-stein, Walk to Marienbruke first, then walk down the path to the castle,. Arrive 20 minutes before your timed entry. Afterwards, you can then just walk back down the path back to your car.

So, to sum up: You can be at the parking lot P4 (or P3, P@ or P1- it's all walkable) at 8:30-8:45 with time to spare. The drive from Fussen is 15-20 minutes. So I would leave at 8 am.

AND Finally, the Tegelbergbahn closes at 4:30 pm, with the last ascent at 4:15 pm. so you aren't going to be able to do the cable cars and the castles all in one day.

https://neuschwansteintickets.com/accessibility.html

@derek

Many thanks for your outstanding tips!

For the castles ... I wasn't sure if their comment, "it is highly recommend being on location at least 1.5 hours before the admission," meant arrival in the parking lot, at the castle entrance, etc. Thank you for saving me from needless wasted time.

Also, thank you for the tips on shuttle up to Neuschwanstein, then walking down to the Marienbrucke, then doing the castle tour. Far more efficient! I'm not intent on walking, just don't like getting stuck in lines for shuttle busses when something is entirely walkable. I like your plan much better!

Trying to squeeze in the Tegelberg Cable Car was looking more and more to be an impossibility. Thanks for letting me know it absolutely is. We are actually avid hikers (notice you're from Walnut Creek ... we backpack a lot in the Sierra) and I'm almost considering scratching going in the castles to do the tours and just viewing them from outside. Any thoughts?

Great point on bathroom breaks and food ... perhaps we don't stay well hydrated because we don't make many bathroom breaks. Maybe 1 or 2 per day. For food, we love visiting groceries and markets for either a picnic the same day or the next.

if you don't go in, then your time is all yours. Go up to the bridge when and how you want, catch the iconic views and get on with the day as you wish. Maybe the sommerrodelbahn, maybe the cable car and the other scenic things on the way to Mittenwald...

I have done the Neuschwanstein tour and felt my time was wasted, others may feel differently, outside would gave been enough for me. I haven't been to either of the two other castles, although I keep getting to the dock of the boats on the Chiemsee so I can get to that schloss but the weather hasn't cooperated - 3 times! One day... maybe this year.

The walk up to/from Neuschwanstein Castle is pleasant, scenic, not that challenging uphill if you are in moderate shape and the Christmas card photos we took with the castle and beyond in the background turned out fabulous. With that said, the castle tour was the most underwhelming tour/visit of any place I've ever visited both in the US and internationally. So, if you don't make the actual Neuschwantstein castle tour, but cover everything else you've planned, you will be perfectly fine, and the drive in that area is really beautiful as well.