Keycaps are easy, anything MX compatible (which is like most of them) will work. Since the V6 is a 100% it's even easier, since it's a standard layout and you don't need to look for extended keycap sets that have keys to correspond to certain layout types.
Switches you need to just bite the bullet every now and then. A tester only will get you so far. Expect to make a few regretful purchases from time to time.