Xeshra: The issue with xEdit simply is: It is mainly developed for the Steam version and all the dependencies are premade in order to work with this version. So in order for the GoG version to work the folder simply either will have to be renamed to GOG Games \Skyrim Special Edition GOG\Data
without the GOG tag (can still copy those files back to the GoG folder if done with the work), or simply use the "command line trick", which is for more advanced users. Screw those devs who fail to support the GoG version.
The Skyrim Engine Fixes works too on the GoG version but the "achievement entry" will have to be deactivated, else all the mods will become deactivated and INITIALLY it is set on "achievements enabled"; which is foolish because there is simply literally no one
using this mod in order NOT TO RUN ANY MODs... so the logical thinking is a bit at a disgrace. An nope... achievements will not work on a modded game, not hard to guess why, so the GoG version got no disadvantage.
The only disadvantage is probably the lack of some newer creations club content, although those content either already has become integrated into the main game (up to 100 mods) or at some point they can be gotten regularily from a mod site. On top of that, the game got a LIMITED (yes even Skyrim) capability to handle mods OUTSIDE of a official game integration because most mods will handle a certain number of handle counts, which is limited to 1 048 000 handles, and as soon as those handles are exceeded or even close to it (1 million is the critical number to watch out for) the game will become unable to handle any more mods. It does not matter the number of ESP or ESL... this is rarely the culprit here... according to my experience. The culprit is either the "handle count" and/or bad/excessive scripts... and as always incompatibilities... nothing else.
Many users was moaning about having issues with modding Skyrim, apparently the GoG version... only to find out at some point they even screw up using "the other approximately better version", and either the game is not really able to become modded or they simply fail... most likely they fail.
Truth is: The GoG version is not any less capable and actually technically identical, with a different EXE that will require some adaption for some mods. Another truth is: Yes, modding of Skyrim can be difficult and problematic for many beginners or simply less experienced peoples but using the correct mods working well together and trying to "build up the minor mods around the huge mods" will go a long way on "how it will work well".
I will probably release a small guide soon on the forum, using my 1079 GoG version of the game... just so no one can say "it does not work", with about 990 000 handles (216 ESP, 163 ESL) and so far running "stable" for me. Yes, generally it is recommended to use as many ESP or in some cases ESM as possible in order to bring those handles down. Although for the mods to work best this is not always optimal, because a ESP will allow for lesser "interaction" with the other mods, so this is always tricky in many cases. There is no ultimate solution, it depends on the mod.
Total size of the modded game is 193 GB and around 300 mods-folders has been used for it. Many mods are already a compilation of a huge amounts of smaller mods and some mods are even inside a "major mod", so the available content is so huge... it could offer several hundred hours for testing out everything else, one of the biggest games i know.
The only mod i am currently unable to get to work is Racemenu, just because this one, already told several times... is version sensitive and the creator so far simply was not updating it. However. i heard even the 1070 update may have some issues, so there was probably a failure. So... currently we can only hope it works out somehow, else someday we have to make a alternate mod because racemenu is simply to important... else no body morph possible.
I think i will not switch to a newer GoG version anymore. Just to much work updating it and making a fresh install of everything else... for as good as no gain with very little, if at all... new content. I am perfectly happy with this version, as soon as the very last mod had been updated somehow.
Stick to 659 and any mod for Steam version 640 is compatible, all that is needed it's the basic mods version dependent replaced for the GoG version.
Now the only problem can be getting USSEP as they already updated and they never leave up the older versions, so some might have to track down how to get the older version but that's about it honestly.
But again only the people who have no clue, feel entitled and levitate above us, since they can't play vanilla, OMG too good for that, even if they have no clue how to mod they HAVE TO have a modded game with no work what so ever,
yet are the ones making stuff up and spewing bs they have no clue about, like the OP has greatly demonstrated.
And that my friends, that's the problem when you ASSume.