I went down the suppressor rabbit hole and ended up with several. I would go with direct thread and avoid the "fast attach" or "QD -Quick detach" style that requires a proprietary muzzle device. I have three "fast attach" style from different companies, and one went bankrupt with Remington so the muzzle devices are hard to find, and another changed their design for a new improved design thus mine are discontinued, and again I gotta scratch one up wherever I can find one. Direct thread eliminates this inevitable hassle, shoulda woulda.
Dead Air makes a fine .22 suppressor, but you can get a Ruger for 1/2 the price. I would start with a .22 and "standard velocity" ammo (which is subsonic) and have fun. You can put a .22 suppressor on a pistol without boosters and pistons and all of that jim-crackery. That crap drives me as crazy as fiddling with friction rings on a Browning A5, and I have two that I love. .22 ammo is filthy, if you're OCD you'll be cleaning your suppressor............... a lot.
For rifle, a 5.56/.223 isn't going to be that quiet because of the supersonic crack, but it'll be quiet enough that you won't need ear protection.
.30 caliber is great because you can jump on the .300 Blackout bandwagon and shoot subsonic, hugely fun and truly silent. And/or get an AR-Upper in 7.62X39 and shoot a lot cheaply, yet noisier.
Oh yeah, let me rant on the AR platform and suppressors, direct impingement = facial gas blast and filthy magazines and filthy ammo in the magazines and filthy brass. Booooooooo
might as well factor in a Griffin Armament SN-ACH suppressor normalized charging handle to minimize the gas blast.
Or piston driven AR upper, or adjustable gas block, or your favorite plan B, or get used to gas blast, wear eye protection, the right eye (for right handed folks) gets a beatdown.
Bolt gun has none of those hassles. .300 blackout (subsonic) sounds about like Pfffft
Pistol suppressor above .22 are not my thing, 9mm suppressor on a shoulder fired gun like CZ EVO, Colt AR9mm, Ruger PC9 is in the fun zone.
Are you going to primarily shoot at a formal range or private property where anything goes?
It's past my bedtime, starting to ramble.