We do not know if his cannonball move is chargeable. It looks to be a basic projectile like many other character's neutral specials. The hitbox is significantly larger than a peanut, will presumably deal more damage given that it's a cannonball, and, yes, does not arc.
Junior's up-b also does not appear to charge and e have no idea to what degree it can be controlled. Diddy's recovery gives him amazing vertical and horizontal momentum depending on how it's angles.
N-air is nothing like Diddy's.
D-tilt looks like a pretty standard d-tilt, to be honest. Many d-tilts are similar because there's only so much that can be done to differentiate them. This is no different.
Down-B does summon something, like Diddy's, however, we have no idea how the Mecha Koopa works. It could be an item, or it could just be a moving hitbox.
I mean, sure there are faint similarities, but you can find similar characteristics between all kinds of characters if you look for them.