I've main Wario'd since the beginning of SBB4, used him in my top 3 during Brawl but he's much more improved IMO.
As for bike mechanics, these are just some things i've noticed:
If you drive directly at someone while on the bike and connect there's more damage done.
If you drive the bike and kamikaze it (jump off midway travel), it doesn't do as much damage but can still hit the opponent.
If you drive off the map and hit someone in air it works.
If you kamikaze the bike and jump off before leaving the map, and the bike crosses paths with an enemy it will not hit them unless they are over the imaginary vertical edge line.
Doing a quick 180 on the bike when hitting someone inflicts a very strong horizontal attack. Whereas driving direct straight on into someone will send them flying northeast/west, a 180 is more linear on the horizontal plane if connects.
If you kamikaze the bike at a medium-slow speed and connect, the bike will chain attack your opponent about 3 times. If you go full speed it's one big hit then falls off the map.
If you pop a wheelie from under someone, it will pop them into the air.
If you pop a wheelie and slam the bike on someone, and it connects at 80% or more it's most likely an automatic KO or can damage someone's shield outright if they're shielding from anticipating the bike.
Wario while on the bike can cancel/overpower a good majority of smash moves. Wario kamikaze'ing the bike can still stop some moves allowing you to do an aerial attack when coming down.
If Wario is knocked off the stage, his bike is one of the best horizontal recoveries and because he moves so fast it takes a perfect player to meteor smash you.
Wario can use one jump while off the map, use the bike, then jump off the bike for an extra jump plus his up b.
One of my favorite attacks with Wario is mid-air biking hitting my opponent, their body trails my bike after I jump off by a foot and I WarioWaft the bike causing a huge explosion and auto-KO in mid-air.
Destroying the bike: If Wario destroys the bike himself with any attack the bike will explode but he won't receive damage. If your opponent destroys the bike with an attack, you both get hurt. If Wario attacks the stationary bike and it explodes next to an opponent, the explosion will cause a huge amount damage and knockout distance. Not as great as an item Bob-omb but as effective.
Eating the bike whole recovers 1%, and once the bike is destroyed the other parts don't stay long enough to make it worth your while.