I meant to ask about your display tank.
If the display tank is not drilled to be reef ready, you will need to use a HOT overflow or get your tank drilled for an internal or external overflow box. If you have a sump, you can hide equipment in there and keep it out of the display.
However, I don't really see any problem for not having a sump. You don't gain that much water volume by adding a small tank like 10 gallon as a sump after all. Having a sump means adding a return pump, which can add heat to the water. That's not a welcome thing in the summer time for a small tank.