Do I need plate mount or PCB mount switches?
The PCB has holes for PCB mount switches but plate mount switches without additional legs also work.
Do I need diodes for the PCB?
The PCB already contains 38 diodes on the left side and 38 diodes on the right side so you do not need to buy or solder them manually. The switch holes are designed such that the diodes will be under the PCB for both halves.
Does the PCB support hot swap for switches?
The switch holes are 1.5mm so Mill Max 7305 and Mill Max 0305 should fit snugly. Kailh hot swap sockets will not work.