Any question answered...

Are there domestic heat pump dehumidifiers?

Yes, most of the decent ones. The fundamental principle of a refrigerant cycle dehumidifier is that it's a heat pump, moving latent heat of vaporisation from the condensate to the ambient air. The Trotec TTK series are good. As heat pumps, they have an efficiency of about 2 (e.g. 250W electricity in, 500W thermal out), although that obviously varies depending on the initial ambient humidity and the target humidity.

À heat pump dryer is basically a big dehumidifier but in a closed loop and all self contained, a dehumidifier is doing the same job but in a room.

A good heat pump dryer will always be more efficient but will cost a lot more than a dehumidifier but you also don't lose a room to drying clothes.

I used a dehumidifier for years but after having a heat pump dryer I'd never use a dehumidifier for drying clothes over one given the choice.