I'm not sure if the RCS between Android and iOS will have end to end encryption as there are rumors that it might not because the version that Google uses in their messages app is some proprietary thing what a surprise! and not an open standard like RCS is supposed to be.
The unfortunate thing is that, with RCS, there would be no incentive to convince people to use Signal. With SMS, the quality just sucks and that is an easy way to convince people to other platforms. But, with RCS, it will be much harder.
I have had people that I regularly text on Signal tell me they can't wait for RCS implementation so they can delete Signal and just text on the default texting app, and that is really worrisome if cross platform RCS does not have end to end encryption like iMessage or Google Messages RCS does, but not enough of a reason to convince average people who don't care about any privacy or anything
I haven't had luck or even tried. Mostly, people won't know what RCS implies. But there are still important differences that Signal brings to the table. Signal is not merely E2EE on communications. Signal is actually a combination of many privacy protocols to ensure private communications, where E2EE is only one of them. They have a lot of protocol innovations in key exchanges, group management, metadata storage, contact discovery, etc. RCS does not guarantee E2EE, it needs to be implemented by the ISPs, so using it you don't really know if the other end's ISP supports it, so the RCS negotiation will downgrade to the common denominator.