Power meter spikes.

A question though : would it be possible to display the power in a 3s / 10s / 30s style; like on my garmin 810. The produced wattage is spiky at best at times, and if you do a workout in zwift, it would help alot to display the 3s avg power, to avoid seeing spikes.

I ride with a Stages Powermeter connected to the Garmin Edge 1000. 

This is no bad idea. Maybe something that you put in the settings page?
1/3/10/30sec variant. For the workout mode the programming shouldn’t be change (still uses 1 second interval) but for a rider on power it could be a bit better to hold a certain wattage without the spikes.

A very strange phenomon I noticed is that Zwift shows my power faster then my Garmin.

When I see by example 200 watt it only comes at my garmin a second of two later.