I am building a 300 (eventually) and I will be running two returns for redundancy. Having two returns isn't the issue with a quiet overflow, it is running a manifold from one of the returns. Each time you adjust the flow to an item on the manifold, the pressure in the manifold changes and then more or less water is being delivered to the tank, and therefore the drain that was adjusted is now out of adjustment.
Think about it as if you were regularly adjusting your return pump, you would have to regularly adjust your drains, well, with a manifold, when you tweak something on the manifold, you tweak the return flow.
Still, it may not be a big issue, because you dont change the manifold items that often (changing reactor media for example). I was just saying I like the idea better of dedicated return pump(s) and a dedicated manifold pump for that reason.
When my L1 died, it made me even more certain that I want two return pumps so that the system will never be "down" due to the malfunction of one.
Personally, I'd get an couple of L1s. The price is WAY better than RD or Abyzz, and the service is great, and if one of them craps out, you have that redundancy. If you were dead set on a SINGLE return pump, then I'd get an RD3 and ball-out.
I cant wait to see your build come to life!