I sometimes watch my neighbours and try and guess how they've set theirs up, and I've seen plenty of highly efficient rooms that are just multiples of 1 move, 1 carry, 1 work, and it looks like that works best when the sources and controllers are close together with plenty of room in the centre for a spawn.

There's this guy near me who has a bunch of his heavy drones (9W, 9C, 9M) go to one source, drink it dry, and then scurry over to the other side to catch the other one before the source counter ticks down. As they're moving to the other side, the spawn regenerates them.

I didn't start in a very good area (sources far from controller on opposite ends), so I've ended up with a production line.