As I understand it, doctrinal education, particularly in the periods before the printing press, was quite poor. With many members of even the clergy having a loose grasp on it all. This led to something like a personalization or localization of 'Christian' rituals. What might some of those rituals have been?
Beyond things like easter and the Christmas tree. What are some more day to day rituals one might perform?
Secondly: what are some antiquated rituals that are specifically Christian in origin that may seem at odds with a modern interpretation of Christianity?
I can only really give examples as to the first part of your question.
Looking at the context of Joan of Arc's cross dressing (c.1429), the cult of St Wilgefortis is used as an example for lay or lay/christian cross dressing. Individuals- particularly women- whose bodies imitated that of Christ, were venerated. This meant bearded women in particular. Now, this is only kind-of localised. She popped up across Europe- but not everywhere, and there were significant local differences. This isn't so much a day-to-day ritual as a localised and personalised form of worship.
Worship was also localised and personalised by the insertion of local notables into depictions of biblical scenes in Churches. Obviously the rich would pay, and their faces would replace those of the saints etc. (not that anybody really knew what they'd look like anyway).
Marian cults were diffused and localised quite easily, particularly those which rested on the testimony of a local individual having seen or spoken to a saint. These places might then become places of pilgrimage, and might be officially recognised by clergy who were often initially sceptical of the visionaries.
I'm afraid that without access to my university library I can't be more specific or detailed in my answers, but as I understand it, these were the kinds of ways that christianity might become localised in France and across Europe.