Get at least 1 Spears gate valve for your main drain, they are pricy but it’s what you want. For flow on your returns and other valves I like hydroseal ball valves.This is the overflow I’m getting.
Fiji Cube Low Profile External Overflow Box 1200GPH
The external overflow box is a popular overflow option for hobbyist to build their tanks into the next level. Fiji Cube’s external overflow box features a slim and safe design that offers another solution to perform your tank build. Features: Slim and compact design to suit any aquarium set-ups...www.fijicube.com
I do plan on having a valve.