Drilling tank

[C&C]

I am looking at drilling my 130 Gallon glass tank. I would like a few opinions about where to drill it for overflows, and do you DIY the overflows or buy them.

What size should I have drilled and what Dia pipe to use?

What type of return pump should I use?

I don't think that I want to drill for returns but I could be pursuaded any thoughts?

My sump is approximately 40 gallons (plexiglass)

Any info would be greatly appreciated.

thanks chris