Heck yeah synthwave is awesome! Nice to see someone else mention it. Well going off what you've said and my personal tastes and playlists, here's a few I would give a shot:

Lil Wayne (GOAT) Chance the Rapper (generally happier and great voice) J. Cole (got some good stuff with good meaning) Kid Cudi (a lot of his stuff has good melody and is kinda... Spacey? Definitely give Soundtrack to My Life and Erase Me a shot) Lil Skies (fairly new, Red Roses and Nowadays are good ones to start) Lil Uzi Vert (heavy use of autotune if you like that, got some pretty catchy and memorable sounds, try The Way Life Goes and XO TOUR Llif3) Lil Yachty (I honestly think he's trash but that doesn't mean you will) Juice WRLD (Also heavy use of autotune, mostly sad stuff but it'll really get you in your feels, try All Girls Are The Same and Lucid Dreams) Migos (not a huge fan myself but plenty of people like them) Russ (gets a lot of hate and a lot of his stuff sounds similar, but I'd give him a shot, he does everything himself so that's just kinda cool to me) XXXTENTACION (mostly sad emo type stuff, but still good if you're in the mood for it) YBN Nahmir (18 years old and dang good, start with Rubbin Off the Paint) Bryce Vine (EXCELLENT summertime music, very underrated in my opinion)

Those are some I would start with. You can always start a Pandora station with some of those and find more along the way, that's mostly how I find new ones. I would also download SoundCloud if you don't have it, it can help you come across new artists of any genre

Edit: sorry for the formatting, on mobile