I think Ludens is right - vices and virtues go to the leader of the stack. I have sometimes noticed a prince getting a "steward" or "builder" virtue when he is not (& cannot be) a province governor but because he commands a stack which includes a governor. I am not sure if these nice virtues carry over to when he becomes king - I guess they do, but whether they add 10% to the kingdom rather than province, I don't know. Strangely, I have not found good leaders to pick up vices from their stack - maybe because such leaders are kept busy fighting and fighting seems to minimise the odds of picking up vices. However, my governors tend to have high acumen, so I tend to keep them out of such combat stacks to keep them safe. I guess if you are building up a province and want the steward/builder virtues, it would pay to keep the governors outside of a stack. Towards the midgame, it tends to be governor vices that are the problem so putting them all in a stack (ideally with the governor of Sinai or some such useless province on top!) might be good.

In a PBM campaign, the first thing I do is think what each province can build and from that assign to each province a role - e.g. Cyrenacia for Saharan cav etc.

I also try to assign 3 or so general objectives for the reign, to avoid being carried away by events and minutae, although I seldom stick to them.

Probably my main tip for efficient campaign play would be to assign at least 3 provinces exclusively to ship building. Crank out ships so that you have one in every sea and with maxed coastal trading facilities, you'll be rolling in florins. This will make it so much easier to accomplish whatever goals you have. You'll also be able to see most of the game world in all it's glory. Plus your coasts will be safe from invasion and you'll have great mobility internationally. The only downside is that AI piracy will doubtless spark some unwanted wars.

Mid-game, I also like to send a priest to every province - for intelligence, to convert unbelievers and to help loyalty in my own lands.