As far as overflow boxes go, I would always opt for overkill. That way if you ever decide you want more turnover ( perhaps at some point, a bigger pump) you have that option to upgrade, without buying both pump, and a new overflow box.
As far as brand I don't think it matters. I had both Eshopps and CPR, both worked well.
The only problem I had with CPR, is it needed help maintaining siphon with either a small suction pump, or what I ended up doing, attaching a venturi line to a powerhead in the tank, which constantly sucked air out of the overflow chamber, and the powerhead adding extra current within the tank.
My CPR was old, and the company may have new options by now.
Below is the CPR with an airline running from a powerhead venturi, pulling air from the CPR overflow.
I always liked overflow boxes with more than 1 overflow port to the sump, that way if one gets plugged you have some redundancy, and can use a larger pump.
My pumps usually were rated at minimum 1200gph, and more often than not, much larger.
And .....It is as simple as getting an overflow box rated to the amount or water your pump pumps. After its going, you can change sump depth by either adding more water to the system, or not. I always like my sumps more full than less, and ran them as full as possible without allowing for them to overflow if power went out.
Below is a sump with my typical depth preference
now the same sump during a waterchange.
You can see I walled off the pump a bit with porous filter block, to keep plants out of the intake (as you can see, it was a planted sump), but the walls were not permanent, and were easily lifted out.
During water changes the water level in the main tank would not change, just the level in the sump, I'd run it down to where the pump was almost sucking air (maybe 2" from the floor) and then instead of adding water to the main tank, new water was added to the sump. I did this because in winter my tap water would be super saturated with gases, and this allowed them to off gas before entering the main tank (preventing gas bubble embolism). And as you know I prefer doing about 30% water changes every day, so running the sump almost dry enabled me to do that volume of changes.