Look for the exact indoor and outdoor model numbers rather than a product-family name alone.
Ask how the equipment is sized for the house and whether existing duct airflow is suitable.
Manufacturer data for the proposed combination is more useful than a claim from a different model.
Request records for the exact combination
Collect complete model numbers for the outdoor unit, indoor coil or air handler, furnace when retained or replaced, and thermostat or communicating control. Ask for the manufacturer performance table or rated combination that supports the stated capacity and efficiency.
Ask what heating and cooling design conditions were used and what evidence supports the selected capacity. Square footage alone does not document envelope losses, solar gain, infiltration or duct conditions. If a contractor uses a load calculation, ask for the result and the assumptions that materially affected it.
For a heat pump, discuss output at cold outdoor temperatures, backup heat, controls and the transition strategy. For a retained furnace or coil, request a written compatibility explanation.