Daoism has a varied concept on soul/s - and different schools have different levels of gradations there. However, everything originates from Qi is not true in the case of Buddhism. Probably some Buddhists in China influenced by Daoist practices may believe so, but this is quite antagonistic to most forms of Buddhism, be it the Sūtrayāna or the Tantrayāna (Intellectual and the Tantra schools).
Also, the origin of everything according to Daoism is the Tao, the ultimate state of Non-Duality. Qi originated from this state as do other aspects of creation. Qi can be described as the energetic nature of the Dao. So, it may not be correct to say everything originates from the Qi.
The Lower Dantien, according to Daoist medicinal texts, is where the unborn receives nutrition during the gestation, so forms the first energetic center and hence also the core one. That initial well of life and energy never dries down even after birth and aging, and it is up to oneself to keep this spring of life strong enough to feed the other two Dantiens.
Another interesting study is of the Zen monks, who meditate with awareness on the belly, without indulging in any specific energetics. Essentially, they rely on their lower Dantien to drive other aspects of alchemy and it does work, though awfully slowly, but avoids various complications faced by other Daoists who jump around without cultivating their lower Dantien sufficiently.