Sebastian, just checked out your models. They are very nice. Easily worth 5-15 EUR.
Can any of the specialists here maybe give Sebastian a clear answer to why quad meshes are better than tris?
From my experience ( I‘m not a pro in this topic ) models with quads are much easier to handle if you want to re-sculpt them, for example bed cloth, curtains, etc.
Some single triangles will also sometimes be visible in some areas when rendered. In C4D normally I delete this buggy single triangle and simply recreate it. Works always.
But that’s only my observation.
I‘m sure more experienced forum members will give you a better explanation.