Doing a little test today. My gear is neo2t fw. 0.32, edge1030 and power2max NGeco power meter. Test is an erg mode and small 36 teeth chainring.
Edge 1030 controls trainer (first numbers) and power2max reads power data (second numbers). Heres the results.
300w=314w 250w=261w 200w=209w 150w=155w and 350w=367w bad results. Tested two neo2t units and both have similar results.
Bigger the wattage is difference is also higher.
Heres the data. Laps 2=300w 4=250w 6=200w 8=150w 10=350w
https://www.strava.com/activities/2873992812/analysis/360/421 (better usage)
https://connect.garmin.com/modern/activity/4263262615
Post here your results.