internal resistance is very close in relation with magnet strength ... stronger magnets in the same frame means lower resistance (if the Kv is the same)
but efficient motor needs proper balance between internal resistence and no load current, or better written, the iron loses and copper loses must be aproximately equivalent, and while we use our motor at relatively high rpm, we typically get good results on motor wit rather lower no load current then internal resistance (AXI, MVVS) compared to low Ri motors with higher Io (MEGA, MPJ) ... while indoor models benefit on low Ri motors, because they run on low rpm ~4000 with large prop
regarding torque ... torque is function of motors Kv and current in winding, so does not matter if magnets are strong or not, if the Kv and current is the same, the torque is also the same (aproximately), the difference is in internal resistance as I wrote which is smaller, and in the no load current, which is higher, so we cannot benefit from stronger magnets, if such motor runs at disballanced configuratin in high RPM, it is just not automatical that stronger magnets give better result