Looks great so far. Using a manifold for reactors is great, I'd definitely suggest that. One thing you'll find you are fighting the most is heat in the tank, less pumps helps that a lot. also, rather than using a ball valve on the output side of the pump, use a Tee that drains back to the sump with a ball valve on it. This way, you are not pressurizing your pump to change flow, you're just dumping more back to the sump.
Look into filter socks as well, easier to clean imo. lots of people use pads, But generally the filter socks seem easier.
the last thing is make sure your ATO sensor is in the return chamber, that's where the water will fluctuate, make it adjustable if possible, i wish mine could move up another 1/2" right now to cut down on microbubbles
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Grizz is right about not needing a refugium if you use biopellets, i do have both though, i think they complement each other, but that's just me. Biopellets don't produce pods, and my refugium is loaded with them. Your output from the biopellets should be close to your skimmer input, so try to line that up in there.