The total output of mines and quarries will be equal for the 1.0 release. The only variable will be how fast you can pull those resources out of the ground and that will depend on the number of serfs you assign to do the work. More Workers = More Output. A tile's food harvest can increase slightly by being near a river.
Food is planted in both the winter and the spring. Crops must be planted, weeded and then harvested. As you indicated, food was a great priority in those days and that is reflected in the game. A great deal of manpower will be needed for the production of food. In addition to crops, livestock may be harvested at certain times. Players are also allowed to trade for food, so if you have a shortfall, you may be able to get help from an ally.
Enemies can pillage both settlements and farmland and gain loot by doing so. Without food, your population's morale will start to fall and eventually everyone will starve or succumb to disease in their weakened state. On the opposite side of the coin, if everyone is fed and happy, production can increase!
