Well, They could create Pseudoscientific Phenomenon like creating a cure to a disease, but there is no actual scientific proof or evidence. They could preform feats that defy physical and natural laws since the results may appear science-based, they function more likely on magic or supernaturality because they don’t follow the actual laws of physics or science.

In short summary they could defy some physical laws which could make you supernaturally very strong but not anywhere near on an Omni level

Basically you can control science that isn't scientific. Like, you know Frankestein right? Science can't really create Frankestein in reality but Pseudscience could.

It's super simple, everybody understands this. It's just fictional science, meaning it can be unrealistic, since you have this power, basically you don't need to be scientific, you can just make it sound scientific in nature.

Some pieces of fiction can be more realistic with it’s science or cosmology and some others are extremely unrealistic (Like some Animes or Cartoon Physics)