Air handlers and furnaces aren't usually used in the same home in Tulsa. If you use a furnace, you most likely don't need to consider an air handler.
Air handlers are often linked with heat pumps and manage airflow around your residence. Some systems also have secondary heating and cooling parts to help the heat pump.
A furnace runs in a different way by blowing warm air into your vents, which move it across your residence. Since furnaces use combustion chambers to produce warmth, they don't need some of the parts you'll spot in a standard air handler.