EDIT: WARNING! IF YOU HAVE A SAVE IN SAVE SLOT A, THIS WILL DELETE IT TO PREVENT DESYNCS! YOU HAVE BEEN WARNED!
After playing through this game, I decided to make a TA of this while waiting for the GBA port of MS1 and to take a break of finding everything in MS Advance.
I am picking the Japanese version since you don't have to do as many levels but the problem is if you really need to kill all bosses or just get to the last level. The world map is quite non-linear if you ask me.
Movementwise, flying is the fastest but it can be quite a hassle trying to actually fly the way you want as you'll ricochet if you hit something and that can be costly.
Speaking of flying, theres a small debate on who to use. Twinbee, Winbee, or Gwinbee. Gwinbee charges up punches the fastest but the time it takes for him to fly and the weapon he gets (baby rattles) do pathetic damage.
Winbee charges up flight speed the fastest but her punches take forever to charge and her whip doesn't do much damage (slightly more than Gwinbee) either. Most levels just aren't meant for flying either.
Twinbee is balanced and his hammer does the same amount of damage as a charged punch, rendering it almost useless. His flight chargeup time between Gwin and Winbee's but you go through 4 frames of not flying.
Theres also the option of using 2 players but 2 players is actually useless because
A) Boss fights would be the same length (think of it like Rockman, gets hit and invulnerable for a few seconds).
B) The only time 2 players actually becomes faster is towards the end and that only shaves off like 3 seconds
C) It'll be too much of a hassle on me and chances are I'll end up cancelling the project.
Another thing to worry about is that each level has a "record time". If you beat it then you get a celebration cutscene and if you beat the record by one second or so then its actually slower but I plan on getting it anyway since I'd rather bore you with "YOU PWN!" cutscenes rather than me dancing to save time.
I did the first level with Twinbee just to give you guys an idea of what to expect, although not all of it is flying.
First level