I just wrap a piece of masking tape a few rounds around the string.I can either slide it or put on another real quick.
A crimp will work but will get chewed up and out of round after several moves.
I like dental floss for a perm. nock.A crimp will move if not very tight and too tight can damage a string.When I use a crimp I gently crimp and tie floss above to make sure it doesn't move on me.
I use a nock point above and under the arrow nock.