Global Pass

Depends on what travelling you will be doing by train. Often it is cheaper to buy normal tickets for each trip direct from the railway companies involved, with large discounts for advance purchase.
You will need to list all the rail trips you are planning, and look up the advance purchase prices on the correct websites (correct = the company running the trains). Very tedious.
Even with a pass, you often have to pay extra reservation fees for the High Speed trains, with normal tickets these include reserved seats where necessary.

I suggest you read this first: https://www.seat61.com/Railpass-and-Eurail-pass-guide.htm#railpass-or-point-to-point-tickets
The same website has lost of useful info.

If you're only traveling in 4 countries, you can choose a cheaper Select Pass to fit those specific countries. Or an even better fit would probably be a Swiss Travel Pass plus a European East Pass. Download the printable version of our Rail Guide if you want to more easily compare pass options side-by-side. You generally won't need any seat reservations in those regions, which makes the passes easy to use.

Buying point to point tickets or daily regional passes will surely be your best bet. What is your itinerary?