With the help of proton, I have now moved to Linux and can't be more happy.
Almost everything is working perfectly and, with a very few exception, i'm able to play with every games on my library. Proton is awesome.

However, I have a big problem to understand why it is so hard to find the proton directory (on compatdata) for my games: I want to backup/move my savegames, add mods manualy, acess to a config file... and there is now way to know what directory is used by each game !
I have to open each directory and guess who is who by checking on appdata, my documents, ...
And it's so much worse when you're using Proton for non steam game. As far as I know, there is absolutly no way to find it !

It looks so simple to give the id or the path to the directory in steam without having to find something on an url... Even better, a simple button on the game configuration (under the scrolling menu for choosing a specific proton version for exemple ?) to open the proton directory of the game ?!!

Why such opacity ?
Proton is an incredible solution but it has a better management on some third party apps like in Heroic Game launcher than in steam...