Same problem here, after a clean reset, my SB2 '15 got even laggier. Switching between Edge tabs, opening/closing a program, etc, will cause the mouse to freeze for like half a second. I noticed this problem constantly when watching streams with Edge, because the mouse freezes every time I switched to another tab. I had to use Chrome now which is slightly better than Edge, but closing a program still makes the mouse unresponsive for a split of a second.
Really hope that someone could come up with the root cause, or Microsoft fixes this issue for good.
Having the same exact issue with my SB 15. For example, when running a YouTube video tab in a tab in Edge and switching back and forth between tabs, I get that half second or so where the computer freezes for a split second. Super annoying. Also, when the fan comes on but is running at low RPMs it has this low pitched hum to it, which is super annoying. Not sure if it's just my unit.