To answer the last part of your post:

So far my experience is that the RCS-iMessage feature is working (or not) depending on the Apple user’s provider. I’m on Android with a “cheap” provider in Canada and RCS-iMessage work with my iMessage contacts that are on major providers but those on cheaper providers don’t work yet.

So if you are on Android and your basic RCS works you should be good.

Canadian here who used both small and big providers with pixel phones (3, 5 and 7 pro) bought directly from Google (not financed through the provider).

Not all smaller providers provide 5G but they all have LTE or LTE+. I had 5G working with my Pixel 5 without issue when I was with one of the large providers. I’m with a smaller provider now on my Pixel 7 pro and have no issue connecting to LTE(+).

But, you also mention the Pixel watch. I never used a watch with a sim card and I have to say that it is not always clear from the provider’s website if they are supported or if they will provide a esim for them or not, and at what cost. This is something that looks a lot more straightforward when with Apple than Android.