I bred, raised, and packed with llamas in the '80s and '90s. We had as many as 18 in our pasture at one time. We never had any problem with dominance in the herd. Once in a while, there would be some jostling, but nothing extreme. They have a strong herd instinct that, I think, prevents this.
Our males weighed between 300# and 350#. Our rule of thumb was, like most animals, would comfortably carry 1/4 of their body weight. I have loaded more, but for shorter walks of 5-10 miles. Before my wife and I had llamas, we were backpackers. The transition was effortless. All of our camping gear was lightweight, which you need to save weight. Two llamas could carry all our gear for a week-long trip into the Bob or Scapegoat wilderness. I even took one of the panniers to all the outdoor stores in Helena, and found a cooler that exactly fit one of the panniers. That allowed us to carry home-made frozen meals, salads, and beer.
Packing with llamas is a breeze. I have been out of the business for 15 years now, so I can't give you any references on where to buy gear, but I'm sure Google can. You will need halters sized specifically for llamas. Lead ropes were 3/4" X 8' soft nylon, with a snap on one end, and a knot tied on the other. Stake-out ropes were 1/4" nylon with a snap on each end. the stakes were 1/4" steel rod, with a loop bent on the end. I tried tent pegs, but they kept on breaking on the rocks when I drove them in the ground. I moved the stakes a couple of feet in the morning and evening, as the llamas would wear them loose. I used a sawbuck pack frame. There also are Decker packs. The packs came with a felt saddle blanket, which was probably not needed for the llamas, but came in handy as a ground blanket for me. The panniers were nylon that I got in blaze orange, as we used them for hunting, as well as summer camping.
Llamas are browsers. They will eat about anything, but grass is best. One acre of irrigated pasture per animal, with 1/2 ton of hay for winter feed. Alfalfa hay is too rich for them, grass hay or grass/alfalfa mix will do.
Llamas have many advantages for packing. First, they walk at your speed. They don't spook as easily as a horse. It doesn't hurt if they step on your feet. They are always alert to their surroundings. Our daughter rode one until she was 5, when she got bored riding all day. A friend used to bring his llamas to shows in his van. For stability, they lie down while travelling.
But the most important thing that I always told people was that I can go anywhere with a loaded llama, that you can go, as long as you don't use your hands to get there. We don't scale cliffs. Also, they don't have the "down genes" to walk down stairs. When we first started packing with llamas, I would always challenge them with obstacles we found in the field. I've high-centered one on a 4' blowdown, and taken another across a scree made of 2'-4' boulders.
On the down side, they do "spit". But it isn't spit, they are actually vomiting the contents of their first stomach. This is easy to predict, as they will give you a "horizontal ear threat", to show they are irritated. If you want more info, I'll gladly give it to you.