Yes, it's true, the bosses of Mighty Gunvolt Burst are not terribly interesting they have no real bearing on the story or even any character at all. Why would anyone want to get a high combo multiplier in this fashion? Achieving a high combo powers up basic shots and that extra strength becomes pretty necessary on boss fights since they are bullet sponges who have an ungodly amount of health to the point that fighting them becomes kind of boring. The idea is to get either of the heroes as close to danger as possible, even if the levels' design does not really facilitate it. The second core feature is the burst combo system, which encourages a fairly risky, yet also unnatural, play-style, which involves shooting enemies to death at point-blank range. Mighty Gunvolt Burst circumvents this entirely by giving an unprecedented amount of control and options to make whatever weapon that could ever be desired and the game is even generous enough to offer over 25 empty slots to use.
Usually, in these kinds of 2D run-and-gun action titles, where the protagonist gains various power-ups, there is usually only a couple actually useful, while the rest are just too situational to really be an asset. At first, it is kind of a lot to take in since it does not fully explain itself, but after a little experimentation, the real genius of the system is revealed. Throughout each level, there are also hidden abilities that can be added to the fairly long list of options that can be altered for the heroes' weapons. Instead, the protagonist's main weapon gets an expandable pool of points that can be allocated to various modifiers, perks or tweaks for their main blaster. Normally in games like this, heroes tend to get a new ability from defeated bosses. The real draw for Mighty Gunvolt Burst is how Beck or Gunvolt can have customisable power-ups. Even the story feels pretty tacked on since it really is inconsequential as the entirety of it is set in a VR training simulation. Aside from some minor story variation and altered text over black screens, there really are no other differences of note.
Don't expect Beck to be doing a whole of dashing into enemies here, though. Both characters have their slight quirks that make them sort of unique, which is representative of their gameplay from their respective titles. In fact, upon starting the game it is not quite clear what franchise this belongs to since both Beck and Gunvolt are pretty much given equal billing. Mighty Gunvolt Burst is not quite a sequel to Mighty No.9 or the Gunvolt games.