Both those things sound good to me, though applying it universally to all ages would be preferred. And I wouldn't characterize it as 'arbitrary' necessarily- I think that if you let everyone vote without any pre-requisites at all your democratic process inevitably becomes a carnival sideshow, a shallow popularity contest where the win condition is to appeal to the lowest common denominator. Some baseline level of knowledge in the constituency would be a big improvement, even if we still have the unavoidable problem of 'who determines the pre-requisites' to grapple with.
Disclaimer: I know practically nothing about Vivek or any of his other positions, and this is obviously just a partisan talking point for him. But that doesn't mean the core problem being identified doesn't exist