Since drop-in visits include playing with and exercising the dog, I'm comfortable walking dogs during drop-ins. If I'm doing three drop-ins for the dog in one day, I'll probably play with the dog (or cuddle--whatever it prefers) for the morning and nighttime visits and then walk it if it needs the exercise during the midday visit. I also check the water bowls and do all the other things the drop-in booking entails. Conversely, when I book walks, I still check the dogs' bowls, give them treats, cuddle, play, etc. Basically, for either booking, I do whatever is needed to make sure the dog is cared for and happy when I leave. For me, the difference is that drop-ins are booked as needed (like when the owners go on vacation here and there) and walks are booked regularly (like several times a week on a set schedule). So I give a slight discount for walks because it's continued business I can count on. But that's just me! Other sitters do it differently.
You do not need to do that now. If there is a drop in request, all you need to do is tap the start walk button for the drop in with the app!