Im having the same issue. bought a brand new 2020 iMac 27in with eith mac OS Catalina, running 3.8GHX 8 core, AMD radeon Pro 5500 XT 8GB. When Illustrator first installed it ran really smooth but it crashed 2 times, one while moving a simple object, and the second time when attempting to save a file.
I'm using CC 24.3
The file sizes dont really matter, if its a simple squre with a solid fill or more complex drawings with text and other things like a gradient or overlays, moving the objects is choppy and slow.
I do remember after the second trash adobe had "fixed" the issue but now its slow and choppy. yes it hasnt crashed since, but its unbarable, espeically when dealing with a client face to face.