I have an older Anker 3 in 1 to charge my iPhone, APP, and Ultra2, but it's slow charging my Watch compared to using the front USB-C port on my Mac Studio.
What 3 in 1 are you using that charges the Ultra in a decent time?
In reply to your thread title, Belkin BoostCharge Pro, it charges pretty quick. I usually drop it on the charger when I wake up (66% to 74%) and charges in under an hour.