I know the GOG version still has some issues, but just so I know, what fix should I use with this specific version ?

I ask this because there are several patches on PCGW and I was wondering which one was the better for the GOG port.

As far as I know, Nemesis' wrapper and ThierteenAG's patch doesn't work with GOG, so, your best bet is to use Steam006's patch. Be warned though, that patch contains false positive. (DLLInjector.exe) You are going to have to make a firewall exception for the file mentioned.

Aside from the general patch, though these are not required, you can use CataBridge's 16:9 FMV movies pack, and Silent Hill Randomizer, which activates the "cut" hauntings.

You can find all of these fixes and detailed information about Silent Hill 4 in the link below. Feel free to check it: https ://www.pcgamingwiki.com/wiki/Silent_Hill_4:_The_Room (Delete one space after "https")