With multiple speedups, I've noticed that the game gets harder than usual around the middle of level four. I avoid them until level seven, where you pretty much need one to consistently dodge the last boss' attacks.
Bomb testing! I ran both of these tests multiple times. Apart from bomb collection, my play was almost identical.
Test 1. Got every bomb; the game is a little harder in levels one and two.
Test 2. Never had more than three bombs. Easier in the beginning, little difference (if any) near the end of loop 1.
So, I collect and hoard bombs. (A qualification. I don't know what happens to the rank if you have a really inflated bomb count. I've never had more than ten at once.)
Does anyone know if the yellow point items affect rank? I've been avoiding them just in case.

Even at low rank, some areas require a fair amount of memorization. If you're having trouble somewhere, let me know and I'll share my strats and routes.