Omnipotent - not; Quinn established that.
He said they werent. Thats not establishing anything, especially since Q has said the opposite in the past.
Plus when pushed on that statement by Tuvock and asked what their vulnerabilities might be if they werent omnipotent, Quinn talks about a lack of manners and morality.
But it does happen by means of technology, which means it's not at all inconceivable to think that Q's proven abilities could be what you get when a species actually understands perfectly how that technology works and has developed a way to control it by thinking (which is also very clearly possible).
Yet there is no evidence at all the the Q's powers are tech based.