Today I rode up Alpe Du Zwift for the first time using my new Tacx Neo 2T with a Shimano 11-speed 11-28 cassette at Zwift trainer difficulty of 100%. On gradients 9% or lower I felt that my cadence and overall feel and comfort was pretty great and controlled.
However when I came across gradients 10%+ my cadence was a bit lower than I would be comfortable with especially as I am planning to complete vEveresting which will include 8.5 times up Alpe du Zwift.
So with a play on Jaws, I think I will need a bigger cog. A 11-32 cassette should be sufficient.