Skatepixie has given a good overview…
I would say though that the LCMS is not so much moderate as conservative, it just looks moderate next to the Wisconsin Synod which is really,
really conservative.
As for which one is closest to the “original lutheran form and faith”, it would depend on who you ask, but I would also point out that there are no huge doctrinal differences between conservative Lutherans, their differences usually have more to do with polity, church government and inter-church relations.
So, doctrinally, there are really only two varieties of Lutheran, the conservative confessional variety and the mainstream, more liberal variety.
But there does appear to be a growing high church movement as well. My concern with them is that like Anglicanism, the interest will be more in form and ritual than in confessional commitment which for Lutherans is very important.
In short, my concern is that High Church American Lutherans may become little more than Anglicans - Lutheran Rite.
It used to be said that there is no such thing as a liberal Lutheran, but that was back in the 50’s.
It’s different now.