I'm looking for that apparently changes how much base culture is produced varying by planet
I think like most people, you're not fully understanding how culture works. In this case, culture DOES NOT change depending on the type of planet the culture center is at. The only exception is the social specialization upgrade, in which case the planets with the most specialization upgrades will be the best, but if you do not get this specialization Terrans/Desert/Asteroids etc. all behave the same with culture mechanics.
What DOES matter (and is not explained anywhere) is how many phase lanes a planet has. Basically planets produce a fixed number of culture, and this culture is divided by the number of planets adjacent to a planet, and is spread equally to all of these phase lanes. For some reason the planet infocard shows the spread to each planet, not the total culture produced. So you will get the highest culture numbers on a planet with 1 phase lane, regardless of planet type, but this culture is only spreading to one planet. An identical planet with three lanes will display 1/3 that number, but its applying it towards 3 planets, so the total culture production is the same.
As for why culture stacking often isn't OP... each time culture has to pass through a planet, it loses a certain percentage of its strength. You may have the perfect culture world in the middle of your Empire, but if it has to pass through 6 planets to get to the nearest enemy world, most of it is probably going to be wasted LONG before it gets there. That's why in general a single culture center every few planets is the most efficient for spreading culture in your own Empire. Granted you might get a planet with a great culture enhancing bonus and an extreme social specialization bonus, so that might change things, but penalty for going through planets will sooner or later catch up with it.