Well, I wouldn't worry about the keyboards...there are oodles of choices out there beyond what Apple offers, and they all work just fine with Apple computers. My sons game (they both have PCs for that, since Apple really doesn't make gaming machines) but before the younger one acquired a PC he had a very fancy gaming keyboard hooked up to his iMac - worked fine. Gamers tend to like the older-style "clacky" keys, btw. They're a very fussy lot - lots of alternatives.
The trouble is - once you've HAD a 5K screen, everything else looks lame. Of course, I've yet to lay eyes on either the 6K Apple pro offering or the Dell 8K option - I'm sure those are lovely too.