Ive tried the mod and i have some thoughts about it.
Kuysting:
Its tails but you can Bubble Shield bounce, has Dash mode and can shoot a Ring..
The "Hold" fly its quite convenient for most of the times since it saves you so much muscle effort by not having to spam click, and also gives you a better chance of survival when you have high ping since once you registered the second button mid jump, you are already safe.
Vanilla Dash mode.. im not really sure about this one but, i guess it could make for a less useless Flight character, since you can only go so fast with Vanilla Tails.
Bubble Bounce, its.. kinda weird with a flying character, as one would usually expect things like a double jump, in case you misscalculated a gap, as a "Save Jump", but its not the worst. Althought i would say i dont like at all the fact its kinda janky, since it kills all horizontal momentum, so it makes it really stiff to maneuver around with it.
The Ring.. this i cannot accept at all. Having a vanilla Ringslinger weapon, and for free its too OP. Maybe if you added a "ring consumption" system, and gave it a bit more cooldown per shot, it could be much more balanced, as you cant just mindlessly spam C1 and win.
While in super he loses the Bounce. I guess it makes sense since you would rather not die accidentally in a Deathpit while super. But can you at least give him infinite flight? (Personal recomendation)
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Alex:
This one is quite a chaotic mess if i must say..
Its not inherently bad, but it seems kind of unintuitive.
Bubble Bounce reused from Kuysting. Still a bit janky to use since it kills all horizontal momentum, or at least it messes real bad with it.
Fly Thok, this is.. quite interesting actually, althought im not really sure about the exact presentation of it being a "Hover Thok", then followed by a regular thok on a third input. It seems kinda really OP. I would make it a "Hold" slow fall, then executing a regular thok when you let go off the jump button.
Double Jump in Tossflag. This one its quite unintuitive, given you already presented a custom ability on a Custom key before. Maybe you can move it to C1 so its more consistent with Kuysting and easier to remember?
While in super the bubble bounce is lost, since its reused code.. You could make a duplicate of the Double jump to give him increased jump height while in super, and for the Hover Thok, you could make it longer, or infinite, since you can cancel it anytime by jumping again while mid flight.