Jet Grind Radio has been my favorite video game ever since I played it as a kid back when it first came out- so I know I'm a little bias but holy shit this game is the best thing I've seen on itch.io. You've done an amazing job and I really can't fathom how 1 person can do all of this. We kind of take it for granted nowadays that 1 indie developer does a bunch of work to make a game but I don't want to take that for granted that's absolutely nuts what you've done is crazy dope and I appreciate it.
Asskissing aside, My suggestion is that I think you stand to benefit a lot just from thinking critically about what you liked about jet grind radio and what you didn't like about it. What did jet grind radio do better than JSRF and vis versa? Get other peoples feedback as well. Personally I enjoyed Jet Grind Radio more than JSRF so your game being closer to that one makes it better. There's a few things you've left out that I'm not sure are left out because this is early access or if you plan on keeping them left out-
Spray Can collection. I think collecting items in any game is just fun and the cans help give incentive/direction on where to go and they can add more variety to the strength and weaknesses of different characters based on how many they can hold. Also red health cans. I'm shitty at video games and I liked them.
Spraying Graffiti- this is the core of the game and I feel like JSRF dropped the ball by making it too simple. Your game feels like a nice inbetween from how complex it was in jet grind radio and how simple it was in jsrf. I would prefer it to be more complicated but thats just my taste. Adding a few directions you can press while pressing down the graffiti button would be cute. Also the camera angles changing around in jet grind radio as you finished a part of a tag- i felt like that really added a lot and made it more fun and satisfying when stopping to do a piece.
The amount of graffiti- Get a bunch. Anything you can't do yourself reach out to other people for show them what you got and they should be happy to be a part of it. Also heres an idea- not just choosing 3 graffiti 1 per size, but multiple graffiti for each size just to give more variety. People who do graffiti don't just spray the same tag everywhere they do a bunch of stuff and when I go paint a town i wanna just paint all sorts of shit.
That's all I got for now! I think you're getting a lot thrown at you so I appreciate you taking the time to read peoples suggestions and consider them.