Shouldn't be any issues using these together at all.
What I would do is use the thick epoxy in the corners to make a fillet joint, then a layer of ACR, a layer of fiberglass cloth, then 2-3 more layers of ACR and you should be done.
After that apply the pond armor before the ACR fully cures and you should be able to apply the PA directly on top of the ACR without sanding to rough up the surface.