Wesley1982 wrote:a) Is the Tibetan dzogchen community a nomadic & travelling group?..
The lineages/traditions which kept the dzogchen teaching alive have been both nomadic and institutional. The original religion of tibet is Bön which yes was practiced by nomadic tribesmen (and non-nomadic I'm sure). Bön predates buddhism by 1,500 years, I believe? It was founded by Tonpa Shenrab. Bönpo dzogchen is essentially the same as buddhist dzogchen (and vice versa).
Dzogchen has also been passed down in the buddhist tradition, mainly in the Nyingma school of Tibetan buddhism. I believe Vimalimitra received the dzogchen teachings from Shri Singha(student of Mañjuśrīmitra) and brought them to Tibet, where they were joined with Padmasambhava's and Vairocana's teachings to create the Nyingma school (consisting of Vimalimitra's Vima Nyingtig, Padmasambhava's Khandro Nyingtig and Vairocana's Vairo Nyingtig).
Dzogchen was also practiced by wandering yogi's who belonged to neither the Bön tradition nor Buddhist tradition and the Dzogchen teaching itself is said to have originated in the kingdom of Oḍḍiyāna (which is generally considered to be close to what is present day Khyber Pakhtunkhwa, Pakistan).
(I'm not scholar so if I'm off someone please correct me!)