A few questions about Germanic tribes (in 2.3)

[athanaric]

Apologies if this has already been explained elsewhere, but the player guide is a bit confusing on this issue. In particular, I'm having issues with one province, where I've established Hermunduri, Suebi, Scythians, and finally Chatti as well. The Steppe Nomadism culture is increasing, but the Pastoral Tribalist one seems to be stagnating at best.

1) Why are the Celto-Germanic tribes slower and more expensive to establish? Do they offer hidden bonuses or more special units (in later releases, obviously) than the others?
2) I've assumed that the more tribes you establish, the more cultural conversion you get. Particularly in light of Nomadic enclaves, which convert in another direction and have to be counteracted somehow (unless there is no third culture present anyway). Is that correct?
3) Do other buildings (e.g. temples) increase conversion for the Suebi (and the Lugians)?
4) The guide states: "Only 1 tribe can exist anywhere at a time,so to move tribes around destroy the tribe building then build the Sweboz Clan Tribal Migration." Yet I could establish the same tribes in multiple provinces, and in fact you're encouraged to do so via the three tribe limit, so that doesn't make sense to me. Or do their bonuses not properly work if present more than once?
5) What's the difference between "major" (e.g. Suebi) and "minor" (e.g. Hermunduri) tribes, do they really allow more respectively less infrastructure, and does it make a difference if I establish one, two, or three of the "major" tribes in the same province?