Tie on...that absolutely, positively don't move!!
I'll bet I don't see a sixteenth inch difference in where my nocking points go from one of my bows to the next... regardless of make.
So if I set them in place when the bow is at the proper brace height, I should never need to move it... and I don't! The way I tie them they are there for the life of the string.
Never noticed that nocking point placement changed if the brace height changed anyway. If the brace height changes, you need to adjust the brace height not the nocking point.
Years ago I encountered some problems with the crimp on brass thingies slipping and I ain't gonna have that. (probably more likely to slip if you put the nocking point under the nock than if you put it above...finger pressure and all that)