Birthright:

A holding in the province where the shrine is, or a scouting unit in an adjacent province, is correct.

That is more meta-knowledge. But you are certainly free to ask people "do you know of a Shrine owned by X in any province"

Non-domain characters don't necessarily have events assigned to them just because they don't have a holding, otherwise there'd be several of them every turn. Also, even if they do have a base of operations, random events targeting holdings still won't target them, they have to have a holding or province to be a target for random domain events.

(A non-domain character can have a capital/base of operations without having any holdings. It means they have put up a building.)

Where can I find what the upkeep is per type of ship?

Coasters and Barges are free. All others cost 0.33(As far as I know)

It is 1/3GB of the unit capacity of the ship

Thanks!

Do illiterate PCs still get to do the free research action from the faith rank thing despite being unable to perform research actions normally, or how does that work?

Yes, think of it as a brilliant insight. However, such characters cannot get any bonuses from buildings/etc

Reminder on BR bards - access to Illusion, enchantment and divination. If a faith has 'bards' as their paladinlike class, they can gain schools the faith-priests have.

They have to pay extra CPs for additional access, right?

Kind of like rangers or paladins having to do the same?