I use BTRFS on my Artix system, Ext4 on my Librem 5, Ext4 on my Devuan laptop and Ext4 on my Pinebook Pro. Basically when given the choice in the installer I choose BTRFS but if the installer doesn’t let me pick I don’t care enough to manually partition. I have had no negative experiences with any file system luckily so I just roll with whatever.

One of the reasons I prefer GOG is that I don’t want to use a client. I prefer to download offline installers and then run my games through Lutris or Heroic Games Launcher.