Just to update, I currently have an empty 20L tank on a stand that would be able to fit a 10 gallon sump at the biggest. I have an AC70 modded fuge hanging on right now and figured that if I could eliminate having it there that would be great. Even with all the reading of different types of sumps I still only have basic knowledge as to how they work and how I would go about building one myself. I know a lot of people recommend drilling the tank but not sure if I want to take the risk of doing it myself.
I am ok with having a HOB overflow just not sure how all those pipes work.
If possible will glass shops usually drill my aquarium if I take it in to them?
How many baffles would be enough for a 10 gallon (3-4) to give good flow?
Would it be better to drill now and get rid of the AC70?
Or keep the AC70 and build an overflow later since I won't be able to drill a full tank?

Sorry for all the questions but I am just wanting to get off on the right foot before I plan on filling the tank. Thanks

Oh and just an update of equipment I have:
20L AGA
Stand
AC70 mod
GFCI Unit
2 Buckets for mixing and siphoning saltwater mix
(1) hydor theo 50 watt in AC70 fuge
(2) jager 100 w heaters
(2) Thermometers
Powerhead for mixing saltwater mix
Salt mix
Test Kit
Koralia 2 (for the meantime till I get the new mp10w es)

Planning on buying:
Refractometer
Vortech MP10
Tek 24" T5
LS
LR
RODI unit