Ride height looks about right. I've got the M-sport and it's a tad lower. Ride quality is always going to be on the stiff side, I moved away from run flat tyres which improved it dramatically, but yes check the rear shocks and springs. It's always subjective when describing ride quality via text, what you find uncomfortable may just be normal to someone else used to a 3 series haha.
If you are planning on running the car anyway (flash or piggyback jb4 style) that would overwrite any previous ecu changes. Stock you should be close to 8psi, if anything has changed it'll be usually running higher. Is the charge pipe stock? I.e. plastic still, or is it aluminium. If someone has turned the car in the past, a charge pipe change can indicate this i.e to handle the extra boost. ..but not always.
Great car, you may want to update to a dual cone intake, then leave it as that for a while and enjoy until you understand what you want to mod later on