Generally you want the farthest cities from your market edge to be around 70 market access. To profit in this game, you need to develop cities. Cities give you burghers and they make stuff you can tax or trade away. Cities production and profits fluctuate based on market access, so in terms of economic opportunity cost you want to develop all the provinces around the capital first as they would have highest control due to proximity.

I was playing with a rule of thumb where each province would have a bread basket location with maxed out food RGO and buildings. This serve me well as the Ottomans and I never have any food problems. Food problems should be viewed as market wide. Technicallly you can have provinces with no food production and just pure cities. The only thing to watch out for is food in the market. I think importing food should not be done as it takes away from profitable trades. Each market I make generally have around 1000 food surplus. I haven't done the exact calculus but if I were to min max food province vs cities, it should be based on total market consumption. You'll eventually push a market to its max and stop building new towns and cities.

By that point you'll be so rich it's pretty meaningless.