Are energy generators still relevant?

I'm asking because I'm making a medium-large ship (320, 110, 80) and since rail mass enhancers alone eat 40k e/s I expect to hit the softcap pretty fast once I install other systems.
Do power generators still work with power transfer beams or is the child>parent power transfer automatic now?

I'm thinking about putting two 30*20*20 generators in my ship.
Any advice on how to get the most out of those dimensions?