There is a lot more freedom to part choices in this game than in Battle Revolution (due to much faster part generation, more useful part drops, and faster part switching), so there isn't really a standard setup. I use different parts (mostly gun changes) for each kind of opponent (and sometimes adjust it for individual fights). However, only one robo body is available in the story, so that limits customization options.
Of course it's possible that there is some optimal setup (notably with the splash gun, which I haven't tested yet), but I don't think so.
3way/gatling early, after that mostly sniper for fights against fast/small robos, stun for the second heaviest kind of robos, rayfall for the champion match, some other specific ones in the evil lair and final tournament
a lot of different weapons are good though, depending on how you play and what the opponents do
I mostly use arc bombs, as they're fast and can allow you to block off opponent's movement. probably don't use them as much as I should
haven't really tested pods much, some seem useful maybe but idk yet
several legs are good depending on opponent, ground/stage, and weapon
For anyone who speedruns this game or has had a time in the main mode of the game, which is the main story mode, there's been a new update. From the time of it's inception back in 2015 by CrystalChaos who created it up until recently, the name of this category was called "Beat the Game".
However, a