1) Most commonly used ones is the Cherry style kind. Signature "+" sign on the keycap.
You also have others for Romer G (Logitech proprietary keycaps) and Topre keycpas.
2) Yes and No. Switches are switches, keycaps are keycaps. Of course there are bundle deals that lets u purchase the keyboard kit + switches + keycaps all together in 1. So yes, as in, switches can come with keycaps if u look for bundle sets. No, as in, no because you usually buy specific switches that u like, and specific keycap sets that you like. Most people just buy them separately.
So for example, I'm currently "aiming" for this particular switch.
Gateron CJ Switches.
RMB134.50 for 35 switches. Excluding shipping.
These don't come with Keycaps, so I have to buy Keycaps separately. And I'm considering to buy either of these 2 keycaps set.
RMB188
Or
Akko Red&Blue Samurai keycaps @ RMB299