Orca slicer, has some test prints. You can run them. I did that, and found that for me and my filament, I more or less used the pla settings wrt fans, iirc.
Orca slicer calibration prints for petg on p1s, 0.6 nozzle - #27 by Destiny but there are other threads with different conclusions.
I sort of based that on the concept that petg was meant to be like pla, but a higher temperature. It worked with that approach for me, back on my ender 3 and Cura slicer, and seems to work now. What I did was good enough, but would benefit from fine tuning. A concensus, on other threads too, was that the bbl studio petg settings were not very good.