Choppy mouse in High Sierra Just did a clean install.
Oddly enough, when booting up, mouse responds immediately. 
But after a while it becomes choppy. I am still setting up the machine, so I have no heavy applications running.

MBP-13" 2015
One of those embarrassing problems once you see the fix.
A very heavy iCloud download was the issue. Just let it download it's thing for a few hours then problem resolved by itself.

Hope this helps anybody else.