as long as both games are running the same patch version it should be possible. if you pick it up on gog then the gog version should see those saves as both versions save them in the same folder under documents

I think it's worth a try, thanks.

I own both Steam and GoG version, and I can confirm that you can run both versions interchangeably, as they both use the same directory for savegames and configuration. This includes the .ini which you've probably modified for the Steam version to keep the game from crashing whenever there's combat.

In other words: you don't even need to transfer saves. Just launch the GoG version and enjoy.

Purchased the GOG version to try. FOMM won't install any mods for the GOG version and comparing the Steam and GOG directories, it's apparent that the folder structures are different,=: FOMM doesn't account for this.

Okay, I can live without better textures, etc., if the GOG version will be more stable.

I start the GOG version without any of my mods. Load in a save at the problematic Outcast Fort - crashes right away just like the Steam version.

I can't help you with the Outcast crash but doesn't FOMM allow you to set the file structure to find the gog version. I'm using MO2 and I can run either game throuogh itl. When I create a profile, it asks to find the game. It defaults to Steam, yes, but allows me to change it to gog. I think you need a newer mod manager.

structure shouldn't be different. that's hardcoded in the engine. plus fomm is very old now and hasn't been very stable in a long time. could try vortex or NMM. or with fallout 3 i'd just install manually. most crashes with fallout 3 and new vegas are related to third party audio / video codecs being installed. i used to use media player classic and that large codec pack for it. but discovered that fallout tried to use them over the stock windows one and would crash my game whenever certain sounds played. other than that maybe try installing the unofficial fallout 3 patch. there's a much newer one available that corrects a lot of lingering issues in the game and even the problems that the older fallout patch caused.