My favorite exercises as well Dolf. You might love traveling pushups also.
Overhand is preferable. Plates can be utilized as strength grows. The point of the exercise is the explosive finish so I wouldn't add weight if it prevents you from exploding to finish. You can also increase the pause count as you become more proficient. The goal of this exercise is to excite fast twitch muscles fibers forcing strength gains. Accomplishing high reps is irrelevant and is defeating the true purpose of the exercise.
Think of it as a Olympic Powerlifter. They are able to skip slow twitch muscle fiber and immediately access fast twitch. The muscles need to be programmed to do this.
Accessing fast twitch develops raw strength. Slow twitch provides for endurance.
You can determine your genetic make up to find out if your are slow twitch dominant or fast twitch dominant by performing the following exercise-
Using a big strength exercise like the bench press or back squat, load the bar to 80% of your one-rep maximum (1RM). For example, if your one-rep max on the bench press is 200lbs, then use 160lbs. Then, do as many reps until you fail or your technique gets really bad.
-Less than 7 reps: fast-twitch dominant
-7 to 9 reps: balanced between slow- and fast-twitch fibers
-More than 9 reps: slow-twitch dominant
The goal of my profession is to design training that allows me to be "balanced".