Regarding RCS and its security, as was said, this is a protocol designed to replace SMS. While it provides the potential for end-to-end (E2E) encryption, what was left unmentioned in MacRumors' reporting is that support for E2E is optional and is left up to the carriers to adopt separately. They can support RCS without supporting E2E, and so far as I'm aware, that's what they've been doing up to this point (I haven't checked in the last year or two, so my info may be outdated).
Regarding Google being able to read your messages, yes, they can, though I don't know that they are. E2E encryption protects you against anyone being able to intercept and decrypt your message, but Google built the OS that runs on Android phones, and an Android is one of the "ends" in end-to-end encryption for RCS, so the message is already decrypted at that point. As such, if Google was so inclined, they could forward a decrypted copy to themselves. By that same token, however, Apple could be doing the exact same thing with iMessages sent via the Messages app. In both cases you still enjoy E2E encryption (i.e. no one in between could eavesdrop), but your OS vendor would have broken your trust by using their control over one of the ends to gain access to something you thought was private. You need to be able to trust that your OS isn't forwarding copies to anyone else, so if you find that you don't trust one or the other vendor for some reason, don't get phones with that OS.