Yes, all EVs have a zero duty rate. You still have to get a new tax disc each year, but the price comes up as zero when you apply for a new disc on online (once you've got the fuel type/tax class changed). I enjoy re-taxing my bike each year
Oddly enough the DVLA didn't ask a single question about the size of the motor I fitted to my bike. That may have changed, but from the information I've been able to dig up, electric motors are assessed on their continuous power rating for regulatory purposes, which is good for us.