First thing you need to know is there are two cycles you can end up on while in transition from 5-1 to 5-2.

Cycle #1: If you hit the screen transition while lasers are being fired in 5-1, the laser turrets' firing cycle in 5-2 will be renewed to fire as if they just started firing their lasers.

Cycle #2: If you hit the screen transition while lasers are not being fired in 5-1, the laser turrets' firing cycle in 5-2 will have their cooldown period renewed meaning their cycle begins at the point where they just finished firing their lasers.

When doing Stage 5-1 optimally in No Wrong Warps category you will often hit cycle #2 during the screen transition. This is ideal due to one of the biggest run killers; the first set of 3 laser turrets in 5-2. Cycle #1 tends to have you coming at them while they are firing their lasers which is a bad pattern. With cycle #2, you have a window of opportunity to sneak a kill on the right turret.

The picture above is the three turrets I mentioned before. The numbers represent the kill order if you get to them fast enough to recieve the window of opportunity. Why this order?

As you can see, the M-308 Gunner is killing off the second turret here. It turns out even when up against the wall you can both destroy turret 2 and dodge the laser with the power beam. However in order to take advantage of this. Turret 1 must be destroyed first. Which is why the critical part is getting to the 3 turrets fast enough to get the ideal part of the cycle where the lasers stop firing briefly.

Which take us to the part right before...the little ship section and their retaliation fire. This part must be done close to optimally to get the cycle for the 3 laser turrets. Now here's what i do...

Enemy #1: Not particularly important enemy to make the cycle but you need to kill more on the right side of so you can dodge the backfire straight down at you.

Enemy #2: In contrast to the first enemy, this guy you will want to hit as far to its left as you can so you both prevent missing him (due to the orange block) and most importantly, it spawns enemy #3 sooner.

Enemy #3: Shoot this guy a little more on its right side so you both dodge the retaliation fire and still gravity flip afterwards to prevent hitting that orange wall in front of you (slowing you down alittle).

Enemy #4: Like the first one, not that important. You're past the important and tough part of this section now, but here you do want to hit this guy as soon as you can so the retaliation fire leaves the screen sooner (thus reducing lag).

And that's pretty much it. The first section before this can be learned simply by watching other runs, the last section is all about taking an intentional hit to abuse I-frames all the way to the boss room and killing turret #3 in the first set 3 laser is all about feel and practice, despite being imo the easiest part to mess up.