Big Sur 11.3 bluetooth and jumping mouse syndrome?

My bluetooth Magic Mouse became very jumpy with the update on my 2015 iMac.

But the same lack of fine control persisted when I switched to an old usb mouse---thought that ruled out a bluetooth problem. And mouse clicks on either have terrible latency.

But my Airpod Pros and a second bluetooth headset now stutter terribly.

I have updated to 11.3.1 without discernible improvement....

Anyone else seen this? Suggestions?