xxSAITANxx: Yeah but renaming the file in the original GoG version caused it to fail to load the level and exit the game...
I've never heard or had that. FWIW, my tips apply to the GOG version from a few years ago running on maybe not the most recent Windows 10 build, but at least the one before that. I imagine that the tips work on the latest versions of both, but I can't say for absolute certain.
BTW, also make sure that you have sound driver set to DirectSound in olcfg.exe.
xxSAITANxx: ...in the unofficial version it warped the graphics whenever you went inside any sort of building.
That sounds like the Direct3D rendering issue. You can fix that by either switching the game to 3Dfx Glide mode in olcfg.exe or by following my guide to fix the Direct3D mode:
https://www.gog.com/forum/outlaws_a_handful_of_missions/guide_for_best_3d_acceleration_settings