I've been into custom keyboard layouts for a couple years now, and from there it makes sense to try different shaped keyboards instead of just different key arrangements. I decided i want a Chouchou keyboard with Taipo and i have questions before i go buy a bunch of parts i don't know how to use.

dlip (who made Chouchou) recommends low profile choc switches and keycaps. I know what a switch and keycap are, and that low profile is just a shorter key than what's standard, but what does choc mean here? This is hard to even research without knowing what non-choc switches are called.

The thumb keys look like normal switches with slightly longer caps, and i'm guessing 1.5U means it's 1.5 units along two of its sides. Is that right?

Is there anything else i need to know about PCBs or QMK? Or about mechanical keyboards in general?