Dragon HYDRA soldiers are old members of HYDRA, turned into dragons by Redhead who used Dragon Serum, created by Eveliina. They don´t lose their human abilities like talk or intelligence. They work in large groups to either bring more soldiers to be transformed, work on center of volcano or patrol their home/follow their leader.
Dragon HYDRA doctor/scientist are old doctors or scientists of HYDRA, turned into dragons, just like soldiers. They work on science stuff and producing Dragon Serum. They remain below Dovan volcano.
Armored: https://www.weasyl.com/~rathaloshunter16/submissions/1977785/armored-hydra-dragons-ref