Great question.
I went from a double boot to the HRT and it was a simple transition.
At first I skied it cranked up tight like a back boot, as I went on with it I slowly did it up looser and looser until it wasn’t like much of a back boot.
Then I switched to a RTP and the transition was seamless.
I believe that if I went straight to a RTP it would have been a nightmare.
Go for the HRT! More ankle flex ion will help your skiing!