Thank you so much for your response.
I recently have purchased an preexisting tank (move was successful so far, 3 days after transporting all livestock well, water levels normal)
It has always been a passion of mine to build a tank of my own, but im using this one as practice, while doing everything in my power to keep the previous owners livestock healthy.
Years ago I designed a sump as I would like to keep all things possibly hidden, hidden, but when i got back into this I saw a refugium at a LFS, but didnt have time to ask about it, and it looked very similar to a sump, but with several of the differences you listed, I just wanted professional clarification.