I'm a mountain biker, so I may have a different perspective. I just flip the bike and dial in the adjustment by eye and spinning the crank. Assuming the derail

I'm a mountain biker, so I may have a different perspective. I just flip the bike and dial in the adjustment by eye and spinning the crank. Assuming the derailleur isn't bent, this is usually just about perfect. I get what you're saying about power being a variable in adjustment, I just haven't found that it's a concern for me. Maybe MTB drivetrains have less flex/are less succeptible to that, or I'm just too unsophisticated to realize :)