Those are 2 very good points there!
I think particularly for the bullet it is slightly more conductive than convective due to the relatively small radius of the drum with respect to advertised batch size (based on my observations of other roasters I’ve used - my opinions only, I may be wrong haha).
As for point 2, if going from 200g ->400g the heat transfer boundary area increases and higher power settings probably won’t be much of a problem and tracing the IBTS curves should be fine, but if going from say 200g → 1kg the boundary area doesn’t increase proportionally with batch size due to the dimensions of the drum and the shape of the bean mass.
But then again its all up to context, a 10min 200g batch of light roasted washed Ethiopian can possibly be scaled up to a 1kg batch with minimal scorching, but It probably wouldn’t work for a natural processed Brazilian…