This is a really great song with a beautiful melody.
It's easy to hear that you have some experience in processing vocals, for your first song with Synth V it sounds really, really good.

My (general) advice, which is much more important than any technical tips:
  • find their "sweet spot". With BIAB, it's easy to transpose a song to where your singer sounds best
  • don't force them to do something they can't do. No processing wizardry will make Billie Eilish a metal singer
  • treat the "voices" like real singers. Give them time to breath. They are not Eminem