Just wanted to leave some comments here to help the discussion
Just in case you are not aware (as what you say is still entirely true for the earlier ones) the later institutions grow independently all over the world in whatever provinces fit certain criteria. Global Trade spreads from all Centers of Trade and even grows slowly in all provinces with trade buildings. Manufactories spread from all provinces with manufactories and so on.
Institution spread is scaled by development. It spreads _much_ faster through high development provinces than it does through low development ones. Even with the exact same conditions being true high development means it is embraced much faster. The money cost is based on how much of your total development lacks the institution so waiting for that spread through your high development areas can certainly be worth it.
Actually loyal burghers help spread Global Trade in their provinces (as you can see in the ingame tooltips), loyal nobles help spread feudalism in their provinces and loyal clergy helps the spread of the Printing Press in their provinces. The boosts may be a bit small though

Diplomatic relations is likely the biggest impact you can have for province to province spread. Friendly (ie not negative relations) countries are the only ones that can spread institutions over water to you and they also have a much higher base spread speed than any other neighbor province would (basically the same as between your own provinces).