If your logged in with Nostr any boost is sent to Nostr automatically and I just assume everyone would want that but I could add a toggle to the boost section for this kind of like fountain has.
For the tagging in the Nostr post when I look up the payment info some of the info that's returned is the persons npub so that's how I can tag myself and Matt in the Nostr post.
I don't plan on showing boost in the app since I'm trying to keep it lean and the Nostr post and tagging kind of solves that for me.
I don't have a Rizful wallet so I'm glad it's working.