AI FTP Detection can handle any differences between the two power meters. This is one of the benefits of using a model as opposed to using an estimate. We don’t simply estimate your FTP based on outdoor power data (which is often reads higher than indoors). Instead, we include your outdoor power data in addition to the various data points we already have to predict what FTP you’re likely able to achieve as a result of the Ramp Test. Therefore, you will be able to use your detected FTP for inside and outside rides.
Because power meters are typically more accurate than smart trainers, I suggest you use the power2max power meter and use PowerMatch for your inside Workouts.
To ensure that the two power meters are reading as accurately as possible, I’d suggest that you calibrate them before each ride and ensure to keep the firmware up to date.
Then take your FTP from indoors, to your outside workouts/ races and pace with that number. Then you’ll get a vibe for if the two power meters are close - which they tend to be.
The best way to manage it I have found is through intervals.icu indoor and outdoor ftp number settings. I have tested this numerous times and my assioma duos read 4% lower than my kickr core and so i adjust the 2 ftp’s and Intervals picks up and adjusts the IF (etc) as the rides come in.
I know it’s not perfect but after years of riding i am pretty good at gauging what the various zones feel like. To answer your 3rd point, i’m not sure there is a solution that i can think of. You definitely can’t test it on the kickr?