The plan was to mount the speakers to the wall, but I think I'll revisit the 'form factor' question some more.
If you want the best two channel sound then keep your speakers away from the wall. When you mentioned the placement advantage of using M22 + sub I didn’t realize you were looking at wall mounting. The real placement advantage in using bookshelf + sub combo in most rooms, especially smaller ones is that you can place the sub for the best bass response while placing the bookshelves for the best soundstage. Wall placement negates the soundstage placement advantage because the reflections off the front wall will interfere with the direct sound arriving at your ears. Moving the speaker’s so the drivers are 3 feet or more away from the wall changes the timing of the reflected sound so your ears don’t confuse it with the direct sound coming from the speakers. However, is safety is your primary concern then you may choose to live with wall mounting.
You can also make or probably buy some outriggers for a pair of tower speakers to make them more stable. Someone here has posted about that recently. I won’t kid you I’ve bumped into my M80s and knocked them over twice because I have them pulled out from the wall. No damage because the floor is carpeted and their flat sides create an air cushion just as they hit, but I wouldn’t want to try that on tile or wood floors.
