I have Affinity Photo and Affinity Designer both, (as well as LR) and I love them! I have never had the cash to pay for Photoshop, so I can't compare them, but I can tell you that Affinity is
worlds ahead of GIMP (which used to be my go-to software.)
Like @mattb123, I mostly just use AF Photo for stuff that LR doesn't do so well. I use AF Designer for graphics work. (It would be the competitor for Adobe's InDesign).
Never tried the focus-stack feature, but I do like its panorama stitcher. It "just works" without any fiddling with settings, and creates good looking results without any visible stitching artifacts.