Trying to understand cameras is wild. Okay. So the Sigma 18-35 f1.8 Art is a super-famous great lense. It is for a smaller sensor-size called APS-C rather than "full frame" which I use. Full frame is of course not the largest sensor size.

Is there a larger variant of the lense? Of course not. Well kinda. The 24-35mm f2. Which is supposedly still noticeably different.

The 18-35 can be used on a full frame but from 24 to 35 apparently. But maybe is better, kinda, anyway?

Exhausting.

@lawik Would you like some advice or sympathy?

@equeroot advice is fine :)
I am leaning towards the fixed 35mm for full frame. Can get it for the right mount. No need for adapters. No vignetting.

Buying nothing would be even smarter.

@lawik @equeroot The "buying nothing" is what I end up with most of the time. I am so picky, I would spend at least 2 weeks watching/reading reviews about different lenses before buying one. I would love to have another long lense and one dedicated macro lense but its a big rabbit hole ...
@phillipp I totally get that feeling. I took myself past it by looking for the premium Canon L-lenses and then buying them used. Now I have all lenses and some more so I can put my emotional and intellectual energy somewhere else.