Hi Alex, I think I understand the difference in the modes now. I’ll link a couple of resources that imho explain it well.
In essence:
RESISTANCE- Fixed brake power (think Shwin Bike etc.) linear power increase with cadence. PROS: Simple to implement. Does not need to be “smart” (like needing to know rider weight/hight/bike) CONS: Does not really feel like riding a bike. Values don’t translate from one trainer to another- 50% brake power on a powerful trainer not the same as on a weaker trainer. Not intuitive (what percent setting in i.e. closest to riding in the flat or say at 7% grade)
SLOPE/SIM- exponential increase in power when going faster. PROS: most realistic ride feel. Speeds/Gearing feel of acceleration should be very close to the real bike. CONS: Needs to be “smart” (know the hight/weight/bike type to compute Crr Cda. Intuitive: Every rider knows what a 7% slope feels like.
LEVEL- exponential increase in power when going faster/spinning faster. PROS: more realistic feel than resistance mode. CONS: values don’t translate from one trainer to another. Not intuitive (what percent setting in i.e. closest to riding in the flat or say at 7% grade)