They do have brakes.
My math depends on the drone and the composition of the shot. Way too many variables but it’s definitely a feel sort of thing that came with lots of practice. Yesterday was extremely challenging. As it first crossed the road it really pushed the drone to its limits. Had to drop altitude and retreat at an angle. I could have got closer after that but no real reason. Between crop and zoom can get the shot I’m looking for. Every now and then I’m ready for a new drone and get really brave.