I've never cooked on a BGE, but had a Primo XL and Jr. Here's my take on the Primos. I cannot speak for BGE's, but I'm sure they're very similar.
These are my opinons and are not written in stone.
Pro's: Very Efficient with charcoal
Pro's: Great 'Grill'
Pro's: Very Easy to clean ash out.
Con's: Oven cooked 'texture' on BBQ when going low and slow.
Con's: Stock Gaskets can and will burn off or fall off. Aftermarket gaskets are a must.
Con's: Gaskets will seize shut due to high heat and or freeze shut in the cold.
Con's: Fire boxes WILL break. Even though you can cook with a cracked box for many years. If you pay $1K+ nothing should break.
Now with all of this said you do NOT need anything special to cook indirect. No plate setter or Guru. Simply make a pile of lump on one section of the grill either to the rear, left or right and put a drip pan underneath the meat. Then light a small spot of the pile with a hose torch or small torch. Close the lid, open top and bottom vens 100% then close 75% once the grill gets to 200*. At this point add your cold meat on the unlit side. Close the lid with the vents closed 75% and leave alone. Temperatures should settle in between 250-300, give it 30 minutes or longer to settle in, it takes time. The more you make adjustments or try to get an exact temperature the more you'll drive yourself nuts. Only make an adjustment if your temps go above 300* or below 200*.