Well control points are only there to fix misalignments (tearing falling apart) or to merge components together (also for setting the scale but that is not this case) a smart number even tho this cannot be said generally is somewhere between 5 and 10 adding too many or too less can result in failure. Also it is important to maintain their accuracy. They don’t slow down or make the process faster by any noticeable amount. Best solution is to keep good overlaps and not changing the height of the camera position too far if you shoot on ground and then do drone photos you should fill the empty space in height, as well as while shooting on the ground you should not take one shot from 1 meter and next one from 10 meters. The detail in the images changes brutally and therefore the features as well. If the shooting is done right the Control points should not even be needed.