Insulation matters more with heat pumps, especially ceiling for cold starts (for descending heat build up from the top) as low temp air heating is not as radiative as IR from traditional heating appliances, or the conventional oil radiators that move air passively.
CO² heat pumps are less impacted due to the much higher air temperature but they are very uncommon for split system (dangerous), and usually used for water heating in AIO unit in a basement.
Had a house electrical failure recently with solar, ran one 18k BTU unit for 60m² on a tiny 5hp Diesel generator sipping 0.4L/hr. (2-4L for Diesel burner in comparison)
These models need proper installation as they use a synthetic proprietary lubricant compared to the commonly used mineral oil, moisture or contamination during tubing installation is a big deal for twin rotary compressors which may reduce service life.