Getting mixed opinions on my Google-fu, some say to give the tree only a few spots to grow, others say to leave them. So what’s Lemmys opinion? Thin at all? If it’s clustered leave one per cluster?
I have two, they are mixed species trees from HD, there’s September ruby red, battleford and good land apples.
Always prune off dead, damaged, and diseased wood. Start there. Then prune stray and inward-facing branches. By stray I mean any stupid growth, like a little twig growing out of the trunk 8" from the ground. As for the inward-facing stuff, you don't want a thicket of interlacing branches in the middle of the tree. Prune most of it out. Also prune out anything that's growing very vertically through other branches.
That's bare maintenance. After that you're pruning for form for the kind of tree it is and the kind of tree you want.
From the photo it looks like you mostly need to clear out some of the inward-facing branches. (EDIT: nevermind, it's too hard to tell from your picture.)
The maintenance prune would probably be fine, but I wouldn't do a hard prune at this time of year. Traditionally, you do your hard pruning during the dormant season, but there's starting to be more advice that a mid-Summer prune is also good.
I think the reason Google isn't helping is because the pruning advice very much depends on the age of the apple, what your goal is, and what kind of apple it is.