I'm pretty impressed with the quality of that Bayite temp controller. The relays in it are robust and commercial quality. Just under $60 off Amazon and it can do a lot.
It was really pretty simple to setup and found it can do a lot. More then I will need it for. It can do a differential from the set value from .1 degree on up. It also handles alarms high and low temp and delay on for compressors.
The temp reading seems spot on with the Ranco which only has a resolution of 1 degree. The bayite was reading 79.1, Ranco (both of them) 79, and Apex 79.3.
For dual stage it will work towards what ever the set point is and deviation. Automatically swiching between heating and cooling.
If you don't have an aquarium controller or you want a redundant heater controller this is another option out there like the inkbirds.
Bottom reading is the set value and top is the actual value. And led to show if its cooling or heating.
The manual goes over a few scenarios and the quick start is a heating only setup.