A few thoughts...
- The Direto has a 'power floor' or 'wattage floor' or whatever they call it which means ERG works better in the small front chainring for most people. 25-29km/h flywheel speed is the zone it works best iirc.. (I'm at 31,000 feet and limited bandwidth to check). So maybe try the FTP step test in the little ring and mid cassette up the back.
- Pair both the Controllable Trainer and Power Source as the Direto. Power matching other power sources "works".. but introduces lag/delay into the process in a number of cases. That plus the stepper motor Elite trainers use can be a wavy path to power smoothness as you've outlined.
- iirc the Elite MyETraining App (which is also their config tool/app) has a 'power smoothness' config option under Advanced Config. You can bump that up so the instantaneous power reported is smoother. Zwift workout mode shows 1s power, not 3s, even when that's chosen for free rides / events. This option in the MyETraining app is purely cosmetic.
- Maybe try Bluetooth over ANT+ to see if there is any difference in the experience. Zwift direct Bluetooth to Windows machines is now a few months into beta, I'd hope it's capable of trainer control by now (I haven't checked).
Shane Miller - GPLama YouTube | Twitter | Instagram | Facebook | Strava | Web