I've done about 10 rotis cooks in the past weeks trying different things. I've made two prime ribs, ribs on the ribolator, and chickens.
I'll tell you what I think and I'm sure others wwill follow...
Drip Pan - absolutely use one. Found this out the hard way this weekend on the second batch of chickens. I forgot to put the pan back in and within about 5 minutes, I had huge camp fire going in my ash catcher (I have an otg) while I was tempted to yank it and throw in the pool, the 30 guests in and around the pool made me think otherwise. I pulled the pan out, went out the screen door added a bit of dirt... we're good.
Banking Coals - this is one of my quandaries but I think I've narrowed it down some. Uniform cuts, like a rib roast or better prime rib, pork roasts etc, work well with coals banked to just one side. Whole chicken, where there's different surfaces, nooks and cranny's, and what not, seem to do a lot better with coals on both sides. At least from my experience.
Drip Pan Goodies - I haven't done any myself yet, but based on the number of recipes for just such things, it's clearly safe and encouraged. Check out
Dad Cooks Dinner for some great rotis recipes including drip pan extras.
The Lid - leave the lid on. The idea is that you're cooking with sorda a modified direct/indirect/convection kinda thing. Lid on. No peeking... and you won't once you get the hang of it.
Hope this helps. Others will have a lot more advice and sounder reasons. Consider them all, and play. You'll find out what works for you.