GlytchMeister
Sorry, I don't personally have any recommendations. A lot of members on here have talked a lot about the Pixel Watch. I don't know if they'd recommend it or not, though.
You can read through some other threads to get a better idea of what people think of different smart watches and their compatibility with GrapheneOS by using the forum search or by clicking this link: https://discuss.grapheneos.org/?q=smart%20watch