Doctrine is defined as the church's positions toward the dogma. They are not absolute truths, as Soloralist Dogma is, but rather what the church believes in, regarding reactions to the truths.
One does not have to believe in the gods to be Soloralist. The mere acknowledgment of the quintessences, moral relativity, corruption, and the history of Micras is all that is needed. Nor is it needed to belief in a theist god(s); it is okay to believe that the gods do not, and never did, interfere with the sapients. Thus, it is possible to be an atheist or agnostic and still be Soloralist. In fact, there is an official form of Soloralism, called Essential Soloralism, whose beliefs are exactly this.
By evangelism, the church means the zealous preaching and advocacy of one's morals. This is frowned upon because one should not change another's morals, as this is a form of quintessential corruption. While it is okay to explain one's own beliefs, or even that of Soloralism, it is not okay to threaten damnation or persist or trying to forcefully convince one's morals upon another.
Regarding Moral Relativity
While moral relativity is regarded as an absolute truth, one does not need to actually follow moral relativity. By definition, all sapients are biased by their own distribution of quintessences. Thus, it is impossible for one to balance zirself without desiring to change one's quintessential distribution, and that is frowned upon via Quintessential Corruption. Thus, it is okay to be biased, and in fact encouraged. One should be oneself and follow zirself's own beliefs that ze had grown up on and learned. It is alright for one to be zirself and to condemn beliefs that ze does not believe in.
Regarding other Religions
Soloralism is tolerant of other religions. As sapience naturally has bias through the quintessences, religion naturally is the celebration of the civilization's quintessences. Thus Soloralism tolerates other religions because they are merely the incarnation of the quintessences of the civilization.