When we were doing our new hvac, I spent a lot of time on:

https://hvac-talk.com

Lots of pros there, very helpful!

In general communicating means the equipment can both send and receive information to and from the thermostat. The communication is done over a proprietary protocol. All the equipment and thermostat has to be from the same manufacturer and be a valid match.

The number of stages and the ability to communicate are separate items. You will have to provide the model numbers of the equipment in order to verify if they will communicate properly.

You will have to provide the model numbers of the equipment in order to verify if they will communicate properly.

This is needed to determine what will work. On most communicating components, there are legacy connections for non-communicating system compatibility. You may be able to run the condenser in 2 stage mode but need the model numbers and manufacturer.

Unfortunately, hvac-talk.com has become a refuge for sanctimonious know-it-alls who rarely now offer any useful help for homeowners.