>walkthrough for those interested
To make my couch pieces, first I made a low poly version which I fully unwrapped and textured.
The couches are made of 2 pieces: the wooden platform and the leather cushion seat.
After the low poly version is fully textured, I duplicate it: with this duplicate I proceed to add loopcuts and overall squish and squash the cushion seat, while making sure the wooden platform part remains untouched. There are some editing methods that will ruin your UVs like beveling, so don't do those when you work on the higher poly version. Me I stuck with loop cuts and proportional editing