Welcome to the thread! I'm happy to meet another Siren fan.
I usually use a 2.5 - 3.0 diameter kanthal coil at 1.3 - 1.5 ohms and vape at anywhere from 10 - 15 watts. The flavor is very good for me, especially after a 24 hour or so break in period for a new wick. The flavor will improve also if you lower your coil a bit. I can't think of anything else to suggest, except to use the smallest afc hole and turn the afc until the smallest hole is half closed. I also usually use juices that are 70% pg, so the flavor is pretty good.
I'm at 50%50% with the liquids, I'll make a batch in the future with more pg and will see if I get more flavor than !!
I've not fully understood the difference in terms of vaping of the inner diameter: does it change much between a 2 ID and a 3 ID apart from the amount of wick you can fit in the coil ?!
Next setup I'm gonna try however is a Clapton, I've read about people getting the best results with that kind of wire !
So far I'm having fun regenerating and I'm getting more and more skilled at each regeneration!