For me the AI seems to actually understand the meaning of my search term and is usually accurate and helpful. It is an improvement over how bad Google had become when it randomly deleted search terms.
Hmm... it doesn't jump for me. There's a fixed amount of space reserved at the top of the screen and the AI overview loads into that. It only expands if you press the "Show more" button.
The UI jumps and everything moves, I now have to wait until it loads. Massive UX mistake, you learn this the first week you make websites ...