Two true statements.Don't wait on them kicking them off the NFA act, not gonna happen.
research the mounting system just as much as the can. Don't get lost in the dB ratings.
As far as #2, if one wants the QD systems, the adaptors across a dozen rifles can cost more than the can itself.
My dealer talked me into the Silencerco Harvester that is rated .300 win mag, and going with the screw on. Just takes a few seconds to remove the thread protector from the threaded barrel and screw on the can.