You're right, every horse is definitely different when it comes to "stall" etiquette.
You already know that stripping the stall when starting with pellets provides the greatest benefit. The stall startup with pellets is the only time pellets make more work, but it is worth it.
If you lined up 10 pellet users they would all have developed their own system over time, but to start, here is our rule of thumb:
12 x 12 stall: start with 5 - 6 bags softened about 50/50. The pellet is much like a sponge, if it is a bit softened to start it will absorb the urine quicker.
You may or may not decide to add another bag after a few days - this depends on how much stall walking or "digging" the horse may do - the goal is to keep a few inches of depth over the mat or floor.
The initial bags won't effect your maintenance numbers if you have good depth. If you have too shallow a startup bed, you'll actually consume more bedding over the year.
"Normal" maintenance for a horse turned out during the day and in at night will be about 2 bags per week. A tidy horse may only use 1 and a horse in stall most of the time could use 4. Whatever the number, it is almost always 1/2 or better what you would have used in a traditional flake shaving.
By the way, for maintenance you don't necessarily have to add water to the pellet. Just be sure that during stall cleaning, the outer edges are pulled into the wetspot areas and new pellets are added to the perimeter.
Keep us posted, thanks again.