My suggestion would be to drill and sump it.
If not then the AIO path would work. I ran small nem and clown setupnwith HOB filter for a long time but problem with active suction of HOB is nem will get sucked into the intake tube, get injured or die, and ruin the party for everyone else in the tank.
You need to have a passive drain system that minimizes nem collateral probabilities.
You won't need much if you do the AIO route. Couple baffles and a backing with a small return but in exchange, you sacrifice realestate and some aesthetics on that tank.
Drilling for overflow box and sump would give you the most flexibility...and sound suppression, imo.