Manual, but based on a standard general base plan (2 x sweet spot, 1 x over/under, 1 endurance). I’ve never really bothered with plan builder, so can’t say if one approach would be better than the other.
I was admitted into the beta December. At the time I was really battling with threshold type intervals, including over unders. AIFTP gave me a significant bump, which resulted in my failing a couple of workouts. Indicated this in the post-ride evaluations and FTP was dropped down.
Suddenly the workouts were just right and I stuck with the program. Long story short - I now fairly comfortably do Sweet Spot intervals at the same wattage where I failed my threshold workouts in December, so I am definitely stronger. Most important, this is also reflecting in my racing results. It seems after a bit of a rocky start the system calibrated and and is now working extremely well for me.