You're absolutely right that the crease is done when the leather is cased. If your creaser just puts a crease parallel to the edge, then you will need to bevel it, probably after making the crease. If you have a creaser, or edger, that rounds the edge, too, there is no need to bevel it. Mine are the latter type. With mine, I still need to bevel the back side and that is done after the leather is dry. See the photos below.
Regarding pressure, I put a fair amount of pressure on the tool. I also go over it several times if needed. When I stamp next to the crease, I usually need to go over it again to re-define the crease.