Yes, you will go to the domestic terminal for MIA.

Domestic security lines at ATL are surprisingly long that early. By the time you get to a hotel, you will get maybe four hours sleep.

I don't know if you can re-check bags that night, or have to drag them to whatever hotel you're at. I suggest one of the four Marriott properties at the GICC train stop. This is the fastest way to the airport.

If you do not have pre-check, the main checkpoint is open 24/7.

https://www.atl.com/passenger-inform...nger-security/