I would think that the Pixel Watch should be fairly generic in terms of what type of phone one has. I don't know Google's penetration into the phone market but I would doubt that they want to limit their watch and its functions to their own phones.
I do have the watch and a Pixel 6 Pro but I'm not aware of any functions that I've used that rely specifically on the Pixel phone.
I have a feeling that you should hear from folks using the watch with other brands of phones. Although, frankly, this subforum does not get a ton of traffic.
Good luck with your decision.