I have a bit of experience here. The junction box itself does not dictate the cover plate. That is to say, you can get any 3 or 4″ round box and in theory put a corresponding cover plate on it that has the appropriate cutouts (outlet, switch, decora, keystone, etc).
That said, I’m not aware of, nor could I find a reasonably priced round cover plate that had either decora or keystone cutouts anywhere online just now, which is what you’d want based on your post.
However: You can get a mudring adapter (like this that changes the junction box opening from round to single gang, and from there you could put a decora plate with the the correct number of keystone openings (eg https://www.monoprice.com/product?p_id=34518)
The problem with this is, ‘mud rings’ by definition are raised about 1/2″ which will make your AP’s not fit flush to the ceiling. Probably not what you’re looking for.
Finally, you mentioned air penetration. Most companies that manufacturer plastic junction boxes will have a product line with a flange and a foam seal around it used in new work construction for exactly this reason. Carlon (made by ABB) is a brand you can usually find available at Home Depot, and they usually stock these in store, however carlon has been having upstream supply chain challenges that has prevented them from readily stocking most big box stores for the last several months, so you may not be able to find this product quickly right now.
All things considered I would probably encourage you just to use a regular rectangle single gang box in your ceilings; once the access points have been mounted you won’t see the box or the faceplate on the ceiling, just the AP. You’re not losing out on much cable space between a round and a square box, and if having extra cable is that important I would encourage a service loop above the ceiling.
Last edit, promise: Look at Platte Electric Supply’s website; they have just about every junction box you could imagine, but beware their pricing; if you can find a local Electrical Supply shop that’d be your best bet.