Cool, a fellow wine user, Special Edition has some issues with wine though, the Script Extender takes a long time to hook the game and I get some crashes (I suspect is the lightning effect) , so combining the 2 issues makes me dread opening the game though I am very tempted to finally reach level 80.

The game I had too much time to play was Gothic for me, this one has no quest markers and I also had no internet so I had to struggle with it but I still have it burned in my memory.

Why use SE? Did it add content?

The game looks better in general, SE uses the Fallout4 engine so most features in Fallout4 are present including 64 bit. Characters are looking a bit better, there is more grass and flowers/mushrooms around you can collect(for alchemy), the lighting looks better. If you don't plan to put many hours then is not worth it, but if you want to put a lot of hours and use many mods then my personal opinion is that is worth it. Modding support for it is good the only issues might be the wine/proton related stuff and the mod manager support issues.

I already have SE, I just wanted to know why I'd ever use it; from what you list it seems like everything can be covered via mods in the regular edition?

It depends , I think some mods might be now onlyu updated for SE , some will also suggest S# because is more stable (on Windows). I think I am not qualified to give a correct answer. I have both installed and setup, it was not easy and I gave up on graphics mods (emb or shaders that come with .dll files).

Now I started maybe 1 year ago a new game on SE, just essential mods for me because I had the bad luck of my game crashing in certain regions of the map when I was around level 30 and I had to give up on the save. I was using those cool mods that improve the cities with new buildings, NPCs and quest. I could not solve that issue and I promised myself that I will play next time only with minimum stuff.

I suggest to ask in winegaming subreddit for more info on what other players are using and what to avoid. If you have both games try them both , no mods and compare how it looks and feels.