No need to optimize the start of the level as you have to wait for the moving blocks to move out of the way (I time that part with the song).

Before the boss, usually it would be ideal to drop dash as soon as possible, but I jump higher to move the screen up and ready for the boss. If you don't do that the screen will move itself up slowly and the boss won't start immediately.

And I take back what I said in the old PB; ideally you want to hit the boss like I did here, but sometimes the boss just won't drop spikeballs, regardless of how you move. No idea why.