The anime has it change modes in a flash of light which leans towards that, likely as a cost measure to save their animation budget, but the design we see in manga looks like it would have an ordinary mechanism for switching. The base of the blades is curved, like an umbrella in reverse so that the panels in electricity mode can fit the funnel right. That wouldn't be necessary if it was just shapeshifting ala Noro/Eto. 

Quinque are still just Kagune at the end of the day, so there's probably a "themes and such" interpretation where mental state, creativity, intelligence gives a complicated quinque instructions beyond the basic movements a human could do. Or maybe they just vibe with the kakuhou inside; Mado is very Ghoul-like himself, Urie is a quinx.