I know a thread for this already exists, but it was made in 2015, and both of the answers to it were rather...vague, and inadequate, with the only one that actually answered the question in a meaningfully-helpful just saying "rocket launcher + 3 plasma beams" without specifying which upgrades to go for, or when.

I tried it once, but the rocket was...way too inefficient to do really anything, so I swapped it out with a Particle ball, and while I did get to LEvel 4 multiple times with that setup, I was never able to get everything, with my best seeing 7 escaping.

Somebody on Youtube has posted a 100% run of every level, but it's very inefficient, and I could tell as early as level 1 life 3 the best way of doing things is not what they did. Unfortunately, the speedrunner whose episode 2 run I followed to finally get that achievement has not yet posted a run of Episode 3, so I'm at a total loss for what to do.

Thus, what's the best loadout for episode 3, and which upgrades should you get for which?