This sonic is good, but he needs a few buffs to make him much better without making him game-breaking.

For starter's, his specials should not clash as often as they do. One instance I've seen often with this is that with KASU HEARTS' Mario character that Mario always ends up with priority over sonic, especially on clashes (this includes Mario's Side-Special clashing with homing attack, Up-Special clashing with Sonic's Down Special and so on.) Sonic should have much more priority over characters when clashing with them in an effort to capture his speed.

His F-Special is almost unusable if your opponent is playing the game, both hitting the enemy, and missing the attack puts you in end-lag which makes no sense as its his boost/spin-dash powered attack, I believe with no boost this behavior is somewhat understandable.
My thoughts on how to help Sonic in this area is changing how it functions with boost.
As the boost meter builds up, this move should have less startup frames, become cancellable after landing it, and have less end-lag on missing and hitting the attack, as well as it doing more damage.
Without any boost meter, even if fully charged the move will do less damage and have a decent amount of end-lag as it does currently.

The next thing I'd like to talk about is his Up-Special.. This move is unbearable to use, and most likely the most important thing that needs a buff. When using this move off-stage, if your opponent touches the ring before you (most likely while they are edge guarding you) you end up dying every time. It is probably the worst move in his kit, which definitely sucks because its his only option of recovery when off-stage. Another problem with the Rainbow Ring is that when hitting an opponent into it, or when an opponent interacts with it (while it still being owned by you) is that the hit-stun is not nearly long enough for you to be able to make use of it, the opponent can attack or use their options again almost instantly after being hit by it.
The fixes I've thought of to these problems could be to give the rainbow ring at least two uses instead of just one so even if your opponent uses the ring before you, you are still able to recover.
The next fix is to give the attack more hit-stun when hitting an opponent into it or when they are injured by your Rainbow Ring.

The last thing I'd like to talk about is reworking enhancing his boost meter and its buffs so that the gain of it is either much faster or makes it more worthwhile
Example for enhancing it: Make the meter be gained much faster from landing attacks, specials, and doing air tricks.
As it stands, even if you do air tricks every two to three hit combo, you are unable to raise the meter to 100%, this happens even when not being attacked by your enemy as the meter does not stay in place unless you string one incredibly long combo together (It starts to decrease immediately after, even if you get hits) The meter should not be drained so much if you are attacked while trying to gain it, this leaves it being impossible to do so.
Once this boost meter is finally filled, it should allow some of his attacks to come out faster (Ex. Homing Attack, and Forward-Special) and with less end-lag than before allowing for better and/or easier combos with this character.

An example of reworking the meter: Make the meter a passive system that you gain the same way, but instead of applying the buffs once its filled, apply smaller versions of this big buff depending on how much of the meter is currently filled, allowing faster movement speed, letting him jog or run without needing to start with the slow walk. Currently, the way Sonic runs, via starting off slow and going fast sadly makes him a slow character to use.
With this rework, it would probably be better to let the meter decrease less from getting hit as mentioned above, though not making it too much easier to gain meter as you've already got more passive speed and less end-lag.

Apologies for this incredibly long text, but I am very passionate about this character and I see just how much fun he can be given proper adjustments. I hope you can understand.