MTW old boy just started RTW - some questions

[Omanes Alexandrapolites]

I beg to differ on this point, if I remember correctly it is not that much a matter of number of buildings of a different culture but of the ratio between those and the ones of your own culture. Though I have to agree that the governor building has a greater effect than other bulidings.
Or am I mistaken? I think I read this somewhere in a guide, even being a quote of a developer.

I'm positive that it's per different building as opposed to the matter of a ratio. Destroying structures does, for me, make a difference to the penalty.

Joooray is right, sometimes demolishing a single foreign building doesn't reduce the cultural penalty at all.

That may be attributable to the cap that's set on the penalty (50%). If your buildings add up to sixty percent, then you will need to destroy/upgrade two buildings to result in subsequent buildings removing the penalty.