Eurail Pass

Its not going to make sense financially unless you plan on going about it like a 1990s college kid without the internet just traveling around mindlessly trying to see things in a paper guidebook.

For your average adult, just buying individual tickets will be cheaper for most trips.

A Eurail Pass is never worth it for shorter trips (1 month or less).

But regional passes need to be considered, especially in Switzerland where train travel is wonderful but crazy expensive. Obviously it depends on your itinerary and what you plan to do, but look into things like the Swiss Travel Pass, Swiss Half Fare card, Berner Oberland Pass, etc. It can get complicated but Rick Steves provides an overview Here.

If you go to Munich, there are also regional passes to look at, such as the Bayern ticket. These will cover train rides in Bavaria, including over the border to Salzberg.

Regular point to point tickets on high speed and international rail trains work the same as plane tickets - purchased several months in advance, they are cheap. But if you wait until the last minute they get expensive.

The key thing to do is plan your itinerary first based on what you most want to see and do and then look into rail passes to see if you can save a little money. Don't fall into the trap of buying a pass and then zooming around all day trying to chase value for what you bought instead of doing what you really want to do.