Regarding the dehumidifier function on heat pumps, it is pretty useless in winter.

Heatpumps have one coil inside, and one outside.

When heating they move heat from the outside coil to the inside coil (warming the house).

When cooling they move heat from the inside coil to the outside coil (cooling the house)

Dehumidify mode works the same as cooling (uses the cold inside coil to condense water from the air) except it is designed to avoid "excessive cooling" (uses very low fan speeds, and some other trick).

Result is that a heat pump in dehumidify mode will use power, dry you house, but cool it down. (perhaps some units alternate between heat and cool? - if so, sounds very wasteful in terms of power)

You would be much better off with a stand alone dedicated dehumidifier with a humidistat so it doesn't dry the house too much (particularly if you can run a drain line so you don't have to empty the tank).

A stand alone (refrigerant) dehumidifier works the same as a heat pump, but both coils are inside. It passes the air through the cold coil (causing water from the air to condense and drain away), then passes the air through the hot coil. Air will leave the dehumidifier slightly warmer than it went in (heated by the electricity input and by the energy release from the "latent heat of vaporization" of the condensed water).

Net result is that your house is dried, and slightly heated.