This is just me & my H.G. Thor-epoxied-fingerboard fretless, but...
As an experiment, I recently went from using Rotosound RS66LDs (which I've used since God was a boy) to lighter gauge Roto RS66LCs.
I immediately noticed that the lighter strings ring/sustain longer.
And I was able to lower my action & thus get more of that fretless buzz/growl (aka "mwah"), as well as getting more note fundamental.
I also immediately noticed that I need to clean up my technique if I'm going to use lighter gauge strings and lower action...
JMHO
(p.s. - I'm staying with the RS66LCs.)