Alright so before you flood your house lets help you out here. You always want water going to sump to be gravity fed. This way if your return pump stops you wont pump water into your sump once the level drops below the overflow. You will never be able to exactly match two pumps for in and out of tank either. Run the hob separately as a backup.
You will need an overflow box if your tank is not drilled. I highly recommend cpr with the small lift pump, it basically makes the failure of the overflow nonexistent as long as you regularly maintain the system. Secondly, you need a sump. You can use a manufactured one or a diy, lots of plans out there. Basic parts are a prefilter, media section, and a mechanical section where your heater and pump go. You mentioned refugium. Typically only used in reef tanks where you want a place to grow macroalgae and microinvertebrates free from predation, aka in a refuge. Unless you have serious vegetarians and you want to use plants to drop your nitrates, then you really just want a sump.
Be sure to match your overflow and return pump well to make it efficient and go as big as you can with sump. Think of it as extra cheap water volume. Also not much of a cost difference between big and small relatively speaking, it is always best to overfilter tanks as well.
Hope this helps some.
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