1. Drooped ailerons are used on full scale aircraft in conjunction with flaps to gain a little extra lift on approach. I don’t think you will find them used in an otherwise clean configuration.

2. Every drop of a wing, or sudden snap is not necessarily tip stall. Anything that produces yaw when operating close to the stall angle of attack can cause one wing to stall before the other resulting in a sudden roll. The stall is not always at the tip, but it will still produce a snap. Full scale aircraft have an advantage in that the pilot is controlling the rudder and doesn’t allow yaw to develop, and many of the larger aircraft have a full time yaw damper that positively prevents yaw. On the other hand model pilots have no way to directly perceive coordinated flight. Some have formed the habit of using the rudder only for small heading changes on short final, while others tend to fly with ailerons only with no rudder input to correct for adverse yaw. Both habits introduce yawing moments which normally cause no problem, but if the speed gets a little too slow, or in presence of gusts it can be enough to trip it over the edge. Keeping the speed up is the simplest way to avoid the problem, but if that is not feasible, a habit of never moving the ailerons without a little rudder may be the solution.