1. Yes, all rimfire suppressors require cleaning due to them leaving lead deposits on the baffles. If you only shoot 17HMR it will require less cleaning than if you shoot a lot of .22LR, but it will eventually need to be cleaned. I tend to disagree with
@hereinaz regarding centerfire suppressors. I have a couple that have thousands of rounds through them and they have never been cleaned. They do weigh a couple of more ounces than they did new, but I have never had a problem with carbon flaking out and getting into the action or other issues that I have read about and my oldest can hasn't gained any weight in years.
2. As pointed out, most suppressors come with HUB mounts now, so even if it has a 5/8-24 HUB, you can get a 1/2-28 HUB to put on it. I like direct thread cans over QD setups for two reasons. First is weight. A DT setup will always weigh less and 2) I have seen more misalignment issues with QD than I have with DT. If you mount a DT suppressor correctly it won't loosen up and it only takes about 5 more seconds to get it off and on over a QD, so the "quick" part of QD isn't all that much quicker.