Note: I didn't want to specify the locations as I didn't want to spoil the game and such :p
Ah yes, that does explain how he gets through impossible places without the items Mario buys :D
I had figured out the wing flapping after a long time of trying to get to the top of the first room with the Fungi brain, while the invisible blocks were triggered by accident. I've only found one place with a fake wall, and 2 places with a fake floor (all within the last area of the game). I've yet to find such a thing, and probably wouldn't bother (unless it helps with the Water Tower later on, which is where I was stuck at; I'm referring to the rearranged surroundings, and the hidden door in the wall) :p
I can assure you that the high jump bug is still around within the game :D
There is one area that you can get locked in if you haven't unlocked the wings (dungeon in the desert), and another area further down (the one with giant snakes) that locks you within the same screen with no hope of getting out :s