plumbing drain and return questions.

[smokinreefer]

hey all,
finally getting around to setting up my 65G.

couple questions, looking for opinions on what size pvc to use.

the tank is reef ready, so the drain is predrilled with 2 holes in the overflow.

the larger of the 2 will be the main drain, 3/4" with a gate valve. second will be used for emergency drain.

I plan to have a manifold set up with 3 or 4 returns coming off my return pump. am I correct in thinking that if I use 1" piping the flow will be wider? as opposed to going with 3/4" where the output would have less spread and have more velocity?

or will the drain not be able to handle the volume of water from 3-4 returns?

return pump is a jebao dc12000. (overkill I know, but its adjustable, and at the price point it was worth it for future proofing)