Title. The gog store page is confusing me

No, Gothic 3: Forsaken Gods Enhanced Edition is a standalone expansion. So it's a different game and does not contain Gothic 3.

Gothic 1 and 2 are fantastic games i think. However, they are quite outdated and their controls are not so great but if that is no problem for you i think it is worth giving them a shot. Many people did not like Gothic 3 because of the bugs it had at release but they should be fixed now. Gothic 3 is quite a different game with more modern controls, however I still think it's a great game even though it is not as good as my favorite, Gothic 2. I can't say much about Gothic 3: Forsaken Gods as i have never tried it however, it was made by a different developer. The Arcania games on the other hand are totally different games and more linear as the first 3 Gothic games. I would not call them part of the Gothic series and don't really recommend them. Hope this helps.

THank you. Does 12/3 have controller support or will I just have to get used to wonky controls?

As far as i know they do not have native controller support however, there may be a work around. The thing with the first two Gonthic games is that they were designed to be played using nothing but a keybord. Therefore you would fight by holding the crtl button and pressing the movement key in the direction you want to swing your weapon. However, you could also use your mouse to look around and the left mouse button insted of ctrl. This is what I did but it still takes a bit to get used to.