What's the difference between a "conventional" muscle and whatever other type you're referring to?
If they're skeletal muscles going from one bone across a joint to another bone, they're pretty much the same everywhere, with minor variations for twitch speed, endurance, staining characteristics, etc..
Conventional is how most of us normally move. In sports it's athleticism and in many aikido contexts, "not using strength" means reduction, by various means, not avoidance. Even full-on faked no touch throws involve some use of the conventional muscles to make Jedi gestures.
The unconventional usage I have come across means the most obvious muscles are flaccid. I mean hanging, or even dangling like Osensei's pectorals while moving powerfully regardless of the attempts of others to prevent the movement. This is kokyu
power (Note: Kokyu does not just mean breath). Some of the IP proponents on this forum seem to have cogent explanations for how it's done.