Well... that is scary.
I have the impression... that a lot of problems here could have been avoided if people just had went to a few therapy sessions.
If I understood it right... X's power is the ability to give its processor the abilities they desire, and I think... access to an external energy source too.
That second part is very important I think, choujin abilities seem to be in nature a connection to some sort of "fundamental source" and the themes of each ability are just the choujins channeling a little part of that source.
The X power allows the choujin to take more from that source and allows them too to develop extra abilities with that surplus energy, or however it works.
That is why some "children" of Zora like Tokio and Palma could develop extra abilities, as they did seem to have the potential to carry X, they could take a little more from the connection they have with Zora.