I have an i7-9700k, think there will be any bottle necking issues, assuming I want to run 1080p ultra settings with the highest possible fps. Also my mobo is an MSI MPG Z390
No.
and RTX 3080 will be an overkill for 1080p gaming. Your desired thoughts can be achieved by 3070 instead.
At higher resolutions I would not expect a bottleneck and if there is it should be negligible.What about for 1440p and 4k?
Bottlenecking! Not by much so far I feel and of course 2560x1440p is the perfect resolution for gaming these days.