If you do pursue the train travel route, you will find a ton of really valuable information in
www.seat61.com.
In many cases, European trains arrive and depart right in the city, rather than the long trek to an airport. Plus no tricky luggage and other restrictions. Plus you actually get to see more country, rather than just clouds. Plus you get to get up and walk around more during the trip.
There even are trains specifically scheduled to work well as an overnight bed. Thus saving the cost of a hotel, and getting your body moved while you sleep.
And don't forget the bus systems. Lots of other good lines, but Flixbus can have some amazing rates. And the buses can have the same advantages as the trains.