Do you notice 120Hz and above when doing office tasks? I'd much rather have improved resolution and PPI rather than 120Hz for that use case.
Yes. Even 90 Hz is a noticeable improvement over 60 Hz. I wouldn’t pick it over high-DPI, though.
100% yes
Yes, absolutely
Very obvious when scrolling text and moving windows around, for example.
any animation work
120 Hz vs 60 Hz? Night and day. Immediately noticeable just by moving the mouse pointer. Would expect improvements in scrolling to be apparent to even the most casual passers-by.
120 Hz can also noticeably improve frame pacing for 24p video*.
120 Hz vs 144 Hz? Barely noticeable when flipping between the two. Not sure if I'd pass an ABX test with 100% accuracy.
Can't speak for 240 Hz or higher, as I haven't used them.
* Though 119.88 Hz is probably a better default for this since most non-DCI "24p" video is still 23.976 FPS; this is changing, but until browsers and streaming apps support VRR for video, I'm not convinced this is a good thing due to the mountain of legacy 23.976 FPS content.