Driving, flying, going by train through Europe

For train travel, this website covers it all: https://www.seat61.com/ Without knowing where you are going it is pretty hard to offer advice. For example, renting a car in one country and dropping it off in another usually is very expensive. But if you're only going to one country, that doesn't apply. Once you select an itinerary, come back and ask questions so people can comment on specifics (don't worry, you'll get plenty of advice on specifics).

Thank you! We are looking at Spain, Switzerland, Italy (Florence area, Tuscany area), Croatia, perhaps Slovenia.

Italy and Switzerland are good pairs, as are Italy + Slovenia and Croatia. I would use train in Switzerland, train + car in Italy, car in Slovenia. In Croatia, it depends.
How long is the trip?

Why fly within Europe, better to pick places closer together and avoid wasting time traveling.

If you drive, except in Great Britain, you will need an International Drivers Permit.
Also, driving in places like Italy can easily result in very expensive tickets due to speed cameras as well as driving in restricted areas.

The trains are good just about everywhere. In some countries you have to validate your tickets prior to boarding.

October is nice, even in Great Britain, France and Germany, but very nice in Spain and Italy.

We rented a car (yes driving on the left) in England in 2017 and spent four weeks visiting S. Wales and England (avoiding London).
We loved the British countryside. Smaller cities and towns are less expensive than large cities like London. Places like York, Durham, the Lake District, Cotswolds, Winchester, Bath, Oxford, Cardiff, Tenby and St. David.

It all depends on what you want to see, how slow or fast you travel, budget and style.

Italy and Switzerland have good train service. Slovenia some train service, Croatia almost no train service.

Drop off fees on rental cars can be high, as is gas, parking, tolls and fines, but there are busses and sometimes a guide with a car.

Can't begin to suggest without more info.

We’re looking at ~4 weeks and a mid- to luxury budget.

This will be too fast for many here, but your intrests are pretty spread out so
Okay a short trip for the list you gave and doesn’t sound like a budget trip, so ….
Save Spain and Portugal for another trip.

Three completely different experiences.

1. Fly into Florence and spend 7 days between Florence and Milan by car.
2. Train from Milan to Lucerne, Switzerland.
3. 7 Days training around Switzerland.
4. Flight from Zurich to Ljubljana (there is one non-stop) is the best use of time I think and it starts the new experience.
5. 14 days down through Croatia to Dubrovnik and on to Ulcinj. This is the luxury part of your journey. Luxury because for about the same cost as a basic tour in Switzerland, you can travel pretty much first class …. Especially after you cross into Montenegro. I would do this with private guides and transfers for the most part. You will be surprised how inexpensive that is compared to the cost of your time in Switzerland. (for this part I know a company that can plan it all for you or plan and execute it for you).
6. Fly home from either Dubrovnik or Podgorica (if you went to Ulcinj.

We are looking at Spain, Switzerland, Italy (Florence area, Tuscany area), Croatia, perhaps Slovenia

That's a lot to see in 4 weeks, but it is doable, although if it were me, I would drop two of the listed countries. There is so much to see in each of them that trying to cram in so many places in 4 weeks would have you running around like crazy. Spain, Switzerland and Italy would work in four weeks, as it gives you around 8+ days in each country, plus the few extra days for travel time you will need.

The other option would be Italy, Croatia and Slovenia, again with the same time frame as above.

I would vote for the train as much as you can, as it will generally be less expensive. Spain and Switzerland, as has been pointed out, have decent train service, as does Italy, and I would opt for train travel in those three countries. I have rented cars and driven in several countries in Europe, but never in Italy. And that is because it is very easy to get ticketed there; sometimes with cause and sometimes not. In many cases, you may not find out about it until months after your trip. I've seen many sad stories here on the forum from RS members who drove in Italy, and I have no desire to try it myself.

That said, it will be much easier to get places in Croatia and/or Slovenia with a car, so it's certainly worth renting one there.

One thing to keep in mind with car rentals is that there is usually a surcharge, which can be quite large, if you pick up the car in one country and drop it off in another. So make sure you take that into account when deciding your mode of transportation.

Thank you for the detailed info!

I would encourage you to start a spreadsheet of all of your desired destinations, including all the sights and activities you want to see/do at each one. This will give you an idea of how much time you need to dedicate to each location. Group according to proximity. Rank according to priority. Any destination that gets cut should be put on a new spreadsheet for planning your next trip. Now you're ready to look at dates (keeping in mind any special events or festivals you want to attend or avoid) and rail/air connections.

For a trip that is very spread out, it might make more sense to rent a car for local sightseeing rather than for travel between destinations.

Have a great trip!

We’ve travelled around Europe by all of those means. The easiest country for train travel was definitely Switzerland. No reservations needed for most trains. If you get a rail pass, you just hop on the next train going where you want to go. Some passes cover boats, gondolas & funiculars too. The train passes are very expensive, as is just about everything in Switzerland.

Be aware that many countries have implemented environmental zones, which restrict access by cars to those areas. If you don’t have the proper permit on your car, you can’t stop in those cities (Strasbourg and Munich for example). If you rent a car in Germany, it will come with the German permit. But it won’t have the permit for France.

Some countries also require the purchase of a vignette, which is a sticker that goes on your windshield. This is in lieu of paying tolls, although there may be additional fees for some long tunnels in the alps.

Different countries have different rules of the road, especially when it comes to yielding and who has the right of way. You need to educate yourself on these rules and remember which rules apply to the country you are driving in. In general, driving is getting more and more complicated!

That said, my dream trip in October would take me through the Dolomites, Austria and Switzerland to experience the fall colors and first snowfall of the season.

The easiest country for train travel was definitely Switzerland. No
reservations needed for most trains. If you get a rail pass, you just
hop on the next train going where you want to go.

For those prices I am not sure the convenience is worth it. While not quite the same, I believe that most train companies will sell you a ticket through their phone App right up until the train leaves the station. Of course no discounts that late I presume.

Be aware that many countries have implemented environmental zones,
which restrict access by cars to those areas.

From time to time its fun to read the posts here “how do I pay my fine”.

Some countries also require the purchase of a vignette,

Yup and not always cheap either. Also in the posts of "how do i pay my fine"

Different countries have different rules of the road, especially when
it comes to yielding and who has the right of way.

We have some strange ones here. Discourages me from driving. And the British drive on the wrong side … ekkkkkk

I generally avoid driving. The places that interest me the most are among the cheaper locations and a car with a driver is generally about the same price as a rental car alone in a place like Austria or Switzerland.

I had not thought of a driver. This is all such good advice!