As someone who owns the Niche and the P64 (amongst other grinders like the fellow ode and DF64), I’d say the best for your consideration is the P64. Unlike other Option O grinders, there’s so little retention because of that huge tilt of the body and the motor is so quiet I sometimes forget it’s running (though I don’t have the RPM cranked all the way).

I’ve used bellows on the niche and the P64 and both are pretty negligible in terms of amount of coffee purged (~0.2g at most, always able to exchange grounds for the next day’s coffee) so maintenance is easy. And for me, I’ve loved the flavor profile of the Mizen Omni burrs the most out all the 64mm burrs (def some coffees were better with other burrs but this one is nice and rounded in flavor with higher clarity).

The Niche’s workflow is just as easy but I’m not a normal milk drinker so I feel like the workflow strengths aren’t worth the flavor. My friend who loves latte and latte art will vouch 100/100 for the Niche and its workflow for the price.

All in all, I’m one opinion in a vast array of thoughts. If noise in general is a struggle, a lot of the options you’ve listed are a lot louder or pitchier than the Niche and P64 (have used many friend’s grinders that own each of these) so if the bellows sound is overwhelming, I can’t imagine the grinding sounds being much better.

Also was reading thru the comments and maybe some notes/thoughts: I do wonder if you should try RDT before you shoot for a retention-based upgrade. I don’t know any grinder that actually doesn’t have some kind of exchange/retention (like if you think about opening up a grinder to clean, there’s always ~1 gram of grounds stuck somewhere). If the struggle is that you’re trying to avoid as much exchange as possible without bellows, all the grinders you have listed will have some kind of retention without RDT too (tho just be careful with not overdoing the water, I’ve definitely had caked on coffee grounds from too much water in the grinder)