I am interested in this run but there isn't much by way of documentation here. Any pointers or guides? I don't understand why the WR doesn't take the green pickups in the first two levels, for example. What is the optimal route, and why?

Sorry about that, I'm not great at documenting things I find, especially when it's on accident.

The avoiding green pickups is because the missiles only fire when the full set is gone whether by off screen or hitting a target, so avoiding the powerups makes it so that it only has the one missile that if you get right up in a strong enemy's face (like a boss) then it'll fire very rapidly. This extra damage though seems to interfere with the near continuous damage from the piercing shot so once you get that there's not a reason to avoid the green powerups anymore.

Similarly the main shot can only have 3 shots on screen at once, but that doesn't matter too much except if you stay too far back with the piercing shot.

As for the route, C is taken over B because it has an extra red powerup, but it can be despawned from a sprite limitation since if I remember correctly there can only be 3 sets of enemies on screen at once, and there's 3 sets of the little blue guys that spawn right before one of the powerup dropper dudes. I don't remember why I took E over F, my notes don't mention powerups and the time is relatively the same, but I noted that F is slightly harder for some reason. I initially was running G as the next stage so that might be it. H is taken because it's about 2.5 seconds faster, or at least that's what I found, I didn't put a huge amount of time into timing it. And lastly J is much faster than K due to the multistage boss in K.

Going H and K gives the good ending and done well K is only about 5 seconds slower than J, but there's no separate category for that and it's not all that different.

Thank you for this post! I appreciate any notes you have and this is already very helpful.

When it comes to the last level, what informs when you pop up to attack? Do you have to kill the hermit crab enemies or is it just easier than avoiding them?

For stage L I didn't do much testing at all, but my guess is there's just an amount of time that needs to pass in order for the boss to spawn as well as having the screen clear of enemies, so using an audio cue from the music for when you need to kill off any remaining minibosses would probably be good. There could also be lag reduction strats, definitely needs to be tested.