I don't have the time at the moment to see what are matches but they need to be matching and by all means TXV.

If you remember many of the older cars with air would freeze you out compared to 80's and beyond because many had an expansion valve of some sort. Newer cars have orifice tubes which are... like the piston setup.

The txv will remove more humidity which will make the comfort level higher and allow a higher comfortable thermostat setting and this will save money and provide more comfort. The unit will also run better and will have the ability to adjust for conditions which will help with longevity.

Piston almost always =builders grade which don't put out stellar numbers.

If it is a heat pump check into demand defrost as an option and variable speed air handler either way or at least the x-13 motor. I have to prepare for a possible long day with a snowstorm coming and working for a utility it might get ugly.

Many in here can roll you through the rest.

"they need to be matching and by all means TXV"

Thanks. By this, do you mean that if the indoor unit has a TXV then the outdoor unit should have one also?

The air handlers are variable speed but demand defrost isn't an option on Carriers (particularly their entry level condensers).

Metering device options are for evap only. Heat pump must be used as shipped. If evaps are TXV equiped,the pistons simple remain packaged and attached to heat pump unused.
Normal to find pistons shipped with heat pumps in case evap isn't being replaced,the new piston replaces old piston if so equiped.