Inside Gaul, the Celtic town network held to a mythology similar to but distinct from the Insular Celtic peoples of the British Isles. Along the Rhine were Germanic-speaking tribes such as the Chatti who would have been very syncretic in lifestyle and religion. In fact, it is the Celtic high god Lugh, himself the embodiment of three separate deities, all resemble and predate "Wodanaz" as a Germanic figure. Resemblances include power of poetry, fury, magic, far-sight, language, travelling, and owning a spear and two ravens. It is likely through Celtic this contact that the first conception of Odin was given to the Germans.
Religious differences existed as well. Caesar might have made up details about the druids, but they existed, and there are almost no hints about a priestly class among German tribes.
While shamans always would have existed in Germanic tribes, there were no such things as formal rituals, such as for the Norse
Vulva, or legal jurisdictions such as the Icelandic
goði. However an early shaman class, the wolf/bear warrior embodying the drug induced ecstasy of self realized war-fury. I believe it is by this war-shaman class that Wodan displaced Tiwaz as alfather.