the best way to figure megaman is to think of it as a game built on trial and error
With
Mega Man 2, one of the (many) problems I found with it is that it doesn't really offer opportunities to test what each of your new weapons does. I mean, as soon as you use it, it starts to deplete its power gauge, and something like, say, the Crash Bomber only has enough energy for six shots!
And then you've got the annoyance of how you can only replenish a weapon
by having it selected. This means that in areas where you can repeatedly gun down enemies for weapon top-up pellets, you've to shoot the enemies to (hopefully) get pellets, then you have to pause to go to the subscreen, select the weapon you want to top up, rejoin the game, collect the pellet, pause, select the Mega Buster again, shoot more enemies to reveal more pellets, pause, select the other weapon again...!
I really didn't like the gameplay mechanics
generally. In fact, because of that hassle with the weapon topping-up...
In theory, I think you can beat all the bosses in Megaman using just the arm-cannon, but I do not like pain enough to put that to the test.
I actually
did just stick to the arm cannon*.
(Did I do a bad thing?)
What I did, actually, was hold the controller a different way for the boss fights, using my middle finger on the A button and my index finger on the B button to free up more opportunities for firing.
I always just get annihilated by minions firing bullets all over the place!
I finished the game with
liberal use of save states, but one of the bosses I could only beat by abusing a bug in the pause menu: every time you unpause the game, Mega Man sort of "regenerates". By rapidly pausing and unpausing at strategic points during the fight, you can get the boss's high-velocity shots to pass right
through Mega Man and take no damage. But for that, I'd never have beaten it.
And yet one of the YouTube videos I watched made dodging those shots look so trivial!
*Except for with Wily, of course. The b*stard.