I’m increasingly of the opinion that these reworked viewing orders are more trouble than they’re worth. There was an argument for it in the days before the ST when a release-order viewing was a bummer because it ended with the PT, but now that there’s another act, I think there’s less reason to break up trilogies. And if we really want to get heretical, I think it would probably be fine for someone with no SW experience who wants to get in on the fun of TROS to skip right to the ST if they’re pressed for time; TFA is pretty much designed to be a secondary entry point.
But yeah. Ideally OT first, and ST is a fine way in as well, but I don’t think the prequels would be terribly compelling to someone not already invested in that world. And in my opinion, which is probably worth less now than it was before I said I support the decision to start with TFA, you shouldn’t go slicing up the trilogies. Experience them each as their own thing.
As for R1 and Solo, I’d honestly save them for later if I was trying to get someone caught up on the Skywalker saga before December. I think they work better the longer you’ve spent in that world, and they’re not directly relevant to what’s going on in the saga, so put a pin in that. You’ve got eight movies to watch as it is. Consider them a nice little treat waiting in the future.