How much pressure when clamping

How “hard” should my dick feel while clamped? Should it be as firm as with squeezes? Or is clamping usually a softer/spongier firmness? When I do squeezes it’s rock hard.

It should feel rock hard, but you can achieve that with medium force clamping. Unfortunately, you will probably have to go overboard a couple of times to figure out what medium force is, but busting a couple of blood vessels is par for the course around here. Just find a clamping pressure where breaking blood vessels does not happen.