I prefer a definition about destructiveness, for example, omega level mutants would be the ones that can destroy earth, or destroy life on earth, unaided, without any enhancement. Maximum level threats.
That would include reality manipulators like Legion when he orginally created the AoA reality, or Iceman who can freeze the whole planet ending life on earth, or Xorn who can destroy earth with a black hole in less than 2 minutes.

I always thought Jean was stronger as a telekinetic than as a telepath. I am pretty sure that has always been the case until Bendis brought her back as teen Jean. I remember Exodus beating her easily a couple of times in the 90s with mind blasts, Xavier attacking her in the Phoenix Saga as Phoenix host and having some effect, and Morrison having her levitate forks and silverware, making it so she could even feel Xavier touching a spoon, as proof of manifestation of the Phoenix. Later in Here Comes Tomorrow, she rearranges the universe moving billions of billions of billions of atoms telekinetically, cutting away a bad future. Cassandra Nova was also a stronger telepath than Jean in Morrison's run. And Cassandra refered to the mind of Charles as the strongest one in the universe.
I dont have a problem with Jean getting power level wank, her problem is the person who brought her back is Bendis, and he is the person who cares the least about continuity, so we have some stuff that contradicts old stuff, and we have to go with it now, because it seems Hickman gave us the official definition of Omega Level mutant to end all arguments.

Exodus does have iirc one of the most impressive showings of telekinesis, he crushed a whole island with telekinesis (I think it was Genosha) and only Hulk prevented everybody from dying, as if a mountain range had fallen over him, and Exodus also repaired the brain of Charles after he was shot by Bishop, only with his telekinesis.