Mechanical Keyboards

As some other commenters said, find a tester and see what you like when it comes to switches.

I'm personally a big fan of linears but I've been warming up to tactiles though I'm a big cherry brown hater.

Atm my main keeb has SP-star tactiles and they feel pretty good compared to other tacts I've tried. (though i haven't tried some all stars like the bobas or holy pandas)

My favorite linears (that aren't in the zealios family) are probably Durock L2s though I'm very partial to Tangerines. Good starter switches are milky yellows and inky blacks as well. You can't really go wrong with cherry reds though.

As to keycaps, You can't really go wrong as long as you find something that'll fit your keeb size. The keychron V6 is a full size board so look for anything that has enough caps for full size boards.

Double shot PBT is pretty sought after for caps because the legends on each key are their own layer of plastic rather than just being painted on like some OEM keycaps. Pudding caps are very nice if you're not looking for anything too expensive or fancy. There's a world of keycap profiles as well, you can take a look here: https://www.keycaps.info/

OEM and cherry profile are what most people are probably familiar with. I heavily prefer SA profile as it's a sculpted profile (meaning it has a nice dip on each key for your fingers.) Though I do enjoy DSA as well. (on DSA profile every key cap has the same shape and height)

I'd recommend you get a nice OEM profile set first though before splurging later on a different profile.