Ive done a bit of high inertia training, and low inertia training on my kickr. What I noticed immediatly was
when spending a lot of time doing lowish inertia training (50 / 28), the large fast group rides I really struggled putting out big power for a long time, and the constant surging nature of those group rides really drained me. On the climbs I was completely fine, and quite comfortable with that feeling of low inertia.
Now I swapped over to tri’s. Im training using higher inertia (53 / 14) as it replicates the conditions closer to a TT effort on a flat course.
I try to replicate the inertia for the course requirements, and dont be afraid to mix it up sometimes. Especially if you only exclusivley train indoors.