OP, if your projector doesn't support ARC, you might spend more to inject one more piece in the chain: a Receiver. The receiver can then forward AppleTV video to Projector and up to ATMOS audio to any speakers (albeit through wired connections). In this exact setup, it would be 2 runs of HDMI from Receiver: one to TV and one to Soundbar.
Among many other benefits- and there's a LOT of benefits with a good Receiver- this would also open the door to letting anything else you'd like to watch on the TV and hear through your speaker(s) vs. being relatively locked down with only AppleTV as a source. Game console? Cable/Satt? Over-the-air free TV? Aunt Meg brings over the old VCR with home movies? Blu Ray Player? CD player? Camcorder? Someone want to show you something on their Android device? Etc.
I am both an Apple everything person and a Sonos person... so I suspect you can really enjoy the Beam. However, given that a projector is usually in play for BIG picture, may I suggest you consider Sonos's bigger soundbar: ARC? Arc will likely bring "bigger" sound to your big picture. Yes, it costs a bit more than Beam but you'll probably enjoy either for 10+ years. If you are ready to buy immediately,
the refurb Arc is significantly discounted for Labor Day weekend making it almost the same price as a new Beam. Sonos refurb is like Apple refurb: seemingly as good as new, same warranty, etc.
Opting for HomePods would definitely be stereo at best and there is not a single rumor about Apple seeking to do anything more than stereo with them. So between those 2 choices, Sonos gives you massive flexibility without much compromise. For example, Sonos works fine with Apple Music (and
dozens of other services too) and works just as well as an Airplay speaker (I do this frequently myself). The HP "smarts" already exist in your AppleTV, iPhone, iPad and/or Mac. For example, on any of those ask Siri to play a favorite playlist of your own creation in the living room and that Beam or Arc will soon be playing that playlist.
Lastly: for someone who is trying to avoid showing ONE wire, this next suggestion probably flops miserably... but again, since you are using a projector for presumably a big visual experience, consider going to the trouble of setting up a TRUE surround sound and/or Atmos system... which cannot really be accomplished by any single speaker/soundbar positioned up front. Marketing for such products pitch ATMOS but that's using trickery to try to fake surround sound. If that worked as well as the real thing, every theater in the world would dump the abundance of speakers positioned all over the theater and put a soundbar down front under/over the screen. That would be far cheaper for theater owners. So why don't they? Because the sound is not nearly as good as the real thing.
True surround or True Atmos needs a mix of speakers- usually "dumb" speakers that can't be made obsolete due to software or walled garden dependencies- positioned all around you and overhead (anyone's ears can certainly hear the difference)... which takes speaker wire runs... which can be challenging to get in place ONE time. In exchange for going to that trouble, your "big" sound will likely best match up to your big picture. That will really maximize a home theater far better than any single speaker/soundbar. It can be a fair amount of trouble once to get it in place but then you get to enjoy it for the next 10-20 or more years. If you are interested but absolutely can't go into the wall for the runs, there are some good options to effectively
hide the wires behind strips that look like moulding if not outright moulding.
