Hi,
Footpods don’t do very well on treadmills.
Basically you’re seeing what mostly happens in that within Zwift you will calibrate it around a certain speed. If you adjust to treadmill too far above or below that speed the accuracy is well out.
Ok if you run at a constant pace but if doing a workout then not so.
You are seeing what i call bouncing where the reported speed constantly flicks around the speed of the treadmill. Partly due to the treadmill but maintaining a constant pace as it slows and speeds up as your foot strikes the belt. The better the treadmill the less this happens.
Only the Stryd would be better accuracy but it’s very expensive and in my experience still wasn’t accurate.
With your footpod you should check the manufactures instructions but in general it shouldn’t matter which foot. I always mount at the bottom of the laces to get the pod as low as possible but again it shouldn’t make any difference to it’s data recording.