What is the difference between Spirit Techniques and Daoist Arts?
The answer is, there's no difference.
Yes, they are just two different names for the same thing. People in the Cultivation World generally refer to it as Spirit Technique because they know that the essence of a Spirit Technique is actually the transformation of Immortal Qi. For ordinary people and Spirit Qi Masters not involved in the Cultivation World, they would call it a Daoist Art because it sounds more imposing.
So, there is no fundamental difference between Spirit Techniques and Daoist Arts; they are just different terms. A Cultivator who wants to pursue cultivation simply uses a set of "basic laws" to forge an immortal body and then employs various Dao Arts and mental methods to consolidate their divine soul.