Welcome to Geekhack!
Looks like the QF Ultimate has a non-standard bottom row, so you'll definitely find it easier sourcing replacement keycaps for the KUL!
I haven't really heard anything bad about the KUL yet, definitely a good keyboard to recommend
![Smiley :)](https://cdn.geekhack.org/Smileys/solosmileys/smiley.gif)
MX reds are a bit too light for me, although my one keyboard with reds is currently doing duty as the keyboard on my gaming PC.
You've heard of the HHKB, right? Topre and 60% in one wonderful package
![Cheesy :D](https://cdn.geekhack.org/Smileys/solosmileys/cheesy.gif)
And if you're going to join a group buy, make sure you have plenty of patience, as they can sometimes stretch out for months!