Swiss gang! Also looking into getting a mech so I do know the feeling
Your only option (unless you want to search for limited run keycaps) is the tai hao blue moon kit, or a blank keycap set. Since the layout is set in software you could technically have any keycaps, aslong as you know where which symbol is.
As for switches, have a look at this handy flowchart, but at the end of the day, it's preference. There isn't really any benefit to any of them concerning gaming.
For the Board, I'd suggest the CU80, which is currently on group buy with a seperate numpad. Otherwise, the GMMK fits the description, but it really doesn't do the budget justice.