The pressure doesn't have to be very strong. The patient should be able to relax into the discomfort. If the pressure is too strong, it will often cause even more muscle tightening. More general massage uses moving techniques, such as strokes, kneading, etc. It can stretch muscles, increase circulation, etc.
Acupressure is really just another massage technique.
It's deceptively simple, but often has great results where moving techniques fail to work. In my opinion, this is because sometimes the patieint is afraid that moving techniques will be too strong or cause pain, so they unconsciously defend themselves by tightening the very muscles that are being treated. With gentle, static acupressure, people are usually able to enter into deeper relaxation. Doing a full-body massage is more demanding on time and energy than a full acupuncture treatment. I have to block out a full hour where I can do nothing else, so massages have to be scheduled separately than acupuncture treatments, and I charge more for them.