I am referring to the physical arrangement of banks of switches (I presume speed controllable MOSFETs, not merely on/off relays) wired to the logic output and controlling the actual 12/24v final power to modules. Are they just laid out dual-inline, like a giant DIP IC or wall service panel? I don't mean to sound patronizing or something, as I presume everyone here understands what a switch is, but I wanted to be clear that I am talking about actual final control, not simply the dumb bus bars that feed them from the supply.
I suppose that this would be about as compact as possible, or is there something that I simply am not familiar with to search for references on?
They're laid out however is convenient for that particular application. Might be a certain way to make contact with heatsinks, or because it makes routing the motor connector easier, or no other reason besides the PCB designer happened to place them in a particular position.
You ask: How is power control handled in serious robotics?" The ones I am familiar are connected to the 480V 3 Phase Bus and follow NEC wiring guidelines. The size of the power feeds depends on the Hp of the motors, hydraulics, pneumatics etc.