Do you honestly think, in the history of humankind, there's never been someone brilliant with super low confidence? Hell, even competent with uncertainty counts as imposter syndrome.
I know countless people that are amazing at something but are super unsure of themselves or don't believe the product of their work is that good.
No, but it’s all relative. Everyone estimates themselves incorrectly at times, but not all the time
Edit to say I know I am mediocre and I don’t fool myself with thinking my lack of capability is imposter syndrome. I think that realization helps me, but ymmv 🤷♀️