For GMK, the kits tend to be bigger due to the way the pricing works with them, much unlike the way Signature Plastics does it.
Generally in GMK, you'll have:
- a base or core kit that covers most common layouts: full-size, TKL, 1800/CP, 75%, 65%, 60%, MX HHKB, etc.
- an extension kit to cover additional keys that are often optional (sometimes 40%s as well), etc
- a spacebar kit
- a novelties kit -- you can choose to integrate these into the base, but keep in mind the number of keys.
Sometimes some kit designers choose to split the numpad from the base kit but this is only really worthwhile when the base kit is expected to hit higher MOQs (500 --> 1000 units for example) as it allows for price cuts that make splitting kits worthwhile. Nearly most of the time, it's better to keep numpad in base on GMK sets.
Anyhow, there are a bunch of keysets out there so check out their kit designs and go from there! This (
https://matrixzj.github.io/docs/gmk-keycaps) should be a good resource to look at recent and older GMK sets.