Indeed I was looking at Tusa Paragon S! Looks like an amazing mask. But then I saw Zensee Pro and it seemed to me like a frameless version of the Paragon S. Also UV and AR coating but lower profile and potentially wider field of view due to proximity to the face.At that price point, I HIGHLY recommend the Tusa Paragon S. Technically it's not "frameless", and everyone's face is different, but I bought one last year and it's the best mask I've ever owned (diving since 1998)....
As far as treating coated masks. NEVER treat the outside of these masks... EVER. Do the inside like you have in the past to get the manuf. coating off and call it good. Also keep in mind that once you start using a coated mask, you are now accepting that you have to be diligent about keeping it in a case or around your neck when it's not on your face. Never drop it in a dunk tank, don't hang it on a first stage or clip to a chest strap on the way to dive sites, etc. Once it's scratched, it's scratched. Having said all that, I LOVE mine and the extra care is okay to me.
So difficult to choose... unlike buying clothes or shoes where you can buy 5 models, try them on, choose the best one and return the other 4 with no hassle, one cannot really try masks this way... the only way to know for sure it take them diving, which makes it inpossile to return. Especially if you do any "treatment" before the dive.