Well...this post reminds me of my own pool project where the shell and coping were the main focus too. It took some patience to get the edges just right, but it was worth it for that clean finish. If you’re working on something similar, the above ground pool forum is full of folks who’ve been...
I used N&C white rapid with their tanking kit on a similar setup and it’s holding up great. Just make sure everything’s clean and dry before you start.