A couple of points. A wing stalls when the angle of airflow (attack) exceeds 16 degrees or so. This is speed independent. That is, it can happen at any speed. (I honestly don't know why 'drag' is brought in as a factor by some in this discussion.)
Secondly, the drag of an airplane is comprised of 1) Form drag (parasite) 2) Skin friction and 3) Induced drag.
It is important to remember that at high speed, the first two predominate, while at low speed, induced drag forms the greatest component. Induced drag, is "induced" at low speeds, because the air starts to spill over at the wing tips, from the high pressure below, into the lower above. Because of the aircrafts forward motion, this turns into wing tip vortexes. The vortexes create the drag with the energy they absorb.
Obviously "spill-over" is worse at higher weights, because of higher pressure differences. I fly "Old Timer" RC, and for duration, we fly not at the best lift-drag ratio, but at the least sink speed. This is close to the stall, and, you guessed it, in the high induced drag range. One way to reduce tip vortexes, is wash out, because it reduces the pressure difference that is the cause of the drag vortexes. And yes, the reduced angle of attack of the wing tips, also means they will not be the first to stall; a much safer way to go.