So probably focus mostly on mineral worlds (since you can get energy more efficiently from the market & food from livestock), with a single food-heavy thrall world (since you can build the 1/planet food boosting building but not the mineral or energy equivalents on thrall worlds). That's why I like Alpine (more minerals on average)
You're right about species-wide population controls. I was trying to micro it via locking down breeding on a planet by planet basis, but species wide makes a lot more sense now that I think about it. You don't get the 20% penalty to whatever you *are* growing, for one.
I think going with wet planet planet type for your primary species is better tbh; They tend to have lot's of food districts which you don't need, so they make ideal worlds to fill with cities and specialist building, and you want city worlds to have good habitability for your specialists and rulers to save on consumer goods and amenities. Habitability for slaves doesn't matter nearly as much, so cold planets are perfect as brutal mining colonies.