Barleyman I thank you again for the reply, and the help. I also found some other information about the possibility of migration.(As far as I know, the following info on the effect that KOE has on Exposition is still valid.
From Discord Soul-Chamber 1.1.18##Selection#
[Covered in SnipeHunters post]
During Domain/Settlement selection the nobility and aristocracy will claim their domains and settlements, which grants them the ability to govern those lands during KoE.
At the beginning of KoE, Nobility and Aristocracy will be required to pick a tribe that matches the starting data as defined in #1 above. However, by using multiple remnants, they can create alternate characters that can migrate from other regions into their domains / settlements and be played.
Over the course of KoE, population, tribes, etc. will shift.
At the beginning of Exposition, the Nobility and Aristocracy will continue their governance by playing the descendants of their remnant ancestors. Through breeding, etc. their bloodlines may be less pure.
Non-nobility/aristocracy can now pick from any families that exist in the domain/settlement, which includes non-standard tribes in the regions as determined through play in KoE).
So I take that one can set it up so they will be able to play the tribe they want, more or less, at the start of exposition.
As far as architecture, you have definitely addressed my concerns, and I am relieved that I will be able to have the ability to design my buildings according to my skill.