I find the notch on my iPhone to be _incredibly_ annoying. It's by far the worst when in YouTube, where it covers a huge chunk of the video and UI elements when not full screened.
The corner of the closed caption button is covered, and it's partially overlapping the radio signal indictators. There seems to be only a very small portion of the bottom edge of the button that responds to taps. It's very hard to tap successfully.
The overflow button is not obscured by the notch, but is partially overlapping the battery indicator. Like the closed caption button, there seems to be only a small portion of the bottom edge of it that will respond to taps.
It's so frustrating.
Here's a screenshot showing it, except for the notch which Apple doesn't include in screenshots: https://i.imgur.com/0KDIWEB.jpg
The notch covers the top half of the Chromecast button, and just touches the top-left corner of the closed caption button (the notch is curving back up, at that point).
Edit: Even zooming in on the video doesn’t hide UI elements only whatever portion of the video overlaps the notch.