Spreading out your guilds is one of the main points Acken makes in his
Liberty Wide Game Guide. I have struggled with that good advice though, because the cap starts out being high production / culture / NC -- it is hard to shift any those roles. Even as the cap is not able to handle them all. I feel like I have better success just running more internal food routes to the cap.
Not mentioned so far is the Freedom tenet which provides extra food for specialists. That helps when your science city (i.e., the cap) is also running four slots for the guilds.
Yes, I want my science cities to be high pop -- but I also want them on mountains for the observatory. So that implies more hills and less farms. So run food routes to observatory cities -- as well as the cap? You don't have enough trade routes! So this all still nets out that most games overloading the cap is not only simplest, but also the only thing that is practical!
I like it when the division of labor falls into place. So I am always looking for an expo on a mountain but with plenty of food and that build Oxford -- I might even put NC there if it will not slow down my early game too much.
If the cap is not coastal, then I look for a great expo that is so it can have EITC, Grand Temple, Iron Works, and Heroic Epic. There is good synergy with those four. Based on this thread, I will be vigilant about stuffing my guilds there too!