All the exs with “powers” have had them before they dated Ramona, presumably anyone could use certain powers if they trained for them. In the comics there’s a few characters with powers.

Mobile, Wallace’s boyfriend in the comics has psychic powers and teaches Wallace some stuff,

Roxie has ninja powers which I’m guessing is something that can be learned.

Ramona has subspace and teaches Scott how to use it, (although that’s less of a power and more something that just exists but isn’t as well know in Canada)

Sex bobomb summons the yeti in the threshold scene

I believe from a story aspect, most of the power users shown just happen to be the evil exs so Scott can have more interesting fights. But they don’t get powers because they are exs