I own both powder cop and lockout, but since using a bullet feed have no station available for a powder checker (LnL AP). I am referring only to handgun cartridge reloading.
The bullet feeder, actually a Bully adapter on the Hornady die and under the Lee four tube feeder set, is up front at station #4, where I can look in the case for powder before pulling the lever for bullet seating. The problem comes with low cc charges in tall, skinny cases. Really good light helps, but with the press on a strong mount you might be on tip toes to look down far enough into the case to see powder. The better solution is to always use powder with a high enough VMD, so the powder level is easy enough to spot. This led me to take an interest in Trailboss, AA#9, Green Dot, and HiSkor 700-x. I am actually using SR4756 in my 357 Magnum Lite, but I gather it is now out of production. I am about to load test rounds in 38 Special using Trailboss, the champ for filling cases enough to see powder.