not much to tell beyond the picture. Some of them are hand cranked, others include e-motors with throttle either because there's legal modes for it or maybe you're at a bikepark where usual public regs against that don't apply.
Mostly niche-builds, so custom things adapted to specific customers or small scale lines
That's true. A bit insensitive of me when I read it now.
Narcolepsy and stuff is straight up dangerous if you're on your own, especially in traffic, assuming you can manage a bike on your own.