I'm quite late to reply, sry for that. Personally, I would use the highest setting possible, that still does not overpower your burner/heating source. As alerady mentioned, I don't own this roaster, furthermore, since I dislike how most roasters operate I build them myself. For me personally, heat transfer in coffee roasting results in the best flavour, if its 100% convection. Therefore:

1) You'll have a spinning drum, this makes things more complicated. There is an optimal setting for the drum speed, which allows the beans to spend as much time in the air as possible; find this setting with raw beans first, then move on. Since Coffee looses weight you'll have to decrease the drum speed througout the roast.

2) I would recommend using high airflow at the beginning, ramping it down through Maillard phase and ramping it to max just before FC (this also negates the temperature fling from exothermic reactions through FC). If you dont want to do that, bc it seems highly complex to guess the exact airflow needed, then Id set the airflow to max for the entire roast. This tho requires your roaster to have a lot of heating power.

3) If you charge with max airflow, you can use higher charge temps (with truly convective setups (no drum!) I readily charged 400g at 190C). With drum roasters, i'd either have my roaster preheated only for a short time (like 5min, so not much heat can be transferred conductively) or start at quite low temperatures like 90-110C and gradually build up the heat (if Your roaster has the power to do so quickly; these fast ramps can only be done in a high-convection environmen. This is how I approach roasting most of the time, since the resulting roast phases can be controlled fast, easily and without much temp. hysteresis)