Is there a fixed location for each OS?

What OS exactly? PoE2 works just as any other game and it installs were you tell it to or where your default steam/gog folder is.

Edited December 27, 20187 yr by Wormerine

If you have it on Steam then just right click on the game in your Library, then select Properties, Local Files, Browse Local Files. I imagine Gog Galaxy or whatever has a similar function, but then GOG also lets you decide where you want to install the game