i answered some of those questions in the wildmana forum:
1) afaik there are no basic effects
2) not all of them, if it adds a promotion the effect is static i.e. unchanged by aura strenght
3) yes, similar to workable city tiles
4) both, depending on the aura
5) you mean the new captains? yes
6) i don't know
7) afaik only indirectly. i think if you focus on certain mana nodes it is more likely that the next research breakthrough will be of this kind of mana.
i am not so sure about some of those question, when in doubt wait for sephi to write his guide.