Ahh I see what you are getting at.
I read an article once comparing the three big staples (corn vs wheat vs rice).
In Europe, wheat was the big staple. It requires a lot of space (hectares/ acres) per kj per person. Rice requires less space per kj/ person, and corn is the best of the three (you get the most kj per acre with corn than you do with rice than you do with wheat).
The problem being that corn is incredibly succeptable to pestilence and disease.
A society based on corn as its staple will accordingly have a ton of the population not involved in farming (and with free time on their hands). The end result will be civilisations rising at a great rate of knots with spectacular technolgical advances in a short period of time, before suddenly collapsing. Those societies will have extremely elablorate priest castes (people with time on their hands devoted to warding off the 'evil spirits' that wipe out civilisation) (Mayans, Aztecs, Incas etc). Their entire culture will focus on 'end of the world' type prohesies and cylical mythos (the Mayan calendar etc).
The technology such a society develops is geared towards wardning off famine and pestillence. An advanced priest caste, and extreme measures to ward off 'end times' (human sacrifice was a big deal). Also astronomy and knowledge of the seasons will get a massive look in.
Society is run by an elaborate priest caste, and wars are fough not for resources, but for sacrifices to keep society running.
Contrast to a society based on wheat. Wheat is very rigorous (compared to corn) but a society based on it pretty much the entire population needs to be involved in its production and harvesting. Such a society will stagnate (there are no free citizens devoted to philosphy, invention, technology and mercantile activities) but it also wont rise and fall like a society based on corn would. It would be more stable, but progress slower. Wheat can also be stored much easier than corn for bad seasons.
The society itself, power projection will be in the form of the distance a man on horseback can ride in a day. Lords will rule lesser lords, who themselves rule even lesser lords like knights. These lesser lords run the system with serfs at its base (owned by the lords whose sole role is to harvest wheat and other crops and livestock). They in turn are protected by the attendant knight or lord in his realm. We called it the feudal system.
The technology a wheat based agrarian society develops will be based around better harvesting wheat. Iron and steel, the plough and the plough horse (and the development of full plate armor and the war horse). Once technology allows for faster and more efficient wheat harvesting, more people will have more time on their hands and the merchant class will rise who (despite not making or producing anything) make money and have spare time. Bang presto, the reneisance happens, technology booms and the population surges.
Rice as the third main staple sits between the two extremes. It produces more kj/ hectare than wheat, but not as much as corn. Unlike corn, it is incredibly labor intensive to harvest reducing its many other advantages. A society built around rice features a combination of things seen in both wheat based agrarian societies and corn based societies, with more reverence for elders (who can organise the complex agriculture and mangagement necessary to harvest rice). In wheat based societies elders neither produce anything of value and are just overall drains on the overall kj needed on society. They tend to get shufffled off when old, and devalued compared to corn and rice based agrarian societies.
You can see from the above that simply deciding on what staple the society uses makes a massive difference to the values, structure, organisation, size, stablity and technology (rate and direction) of a society.
Now add magic.
With magic able to stop famine and pestilence, rapidly grow crops and protect them from plauge and pestilence, or preserve them indefinately you onlly require 1/10 of the (ostensibly agrarian) population required to feed the other 9/10. Technology booms faster than it did in our own reneissance (and as fast as it does now in the 20th century, if not faster). A lot of people have a lot of spare time on their hands suddenly. More ideas, and a sudden rise in the merchant class follows. The merchant class is again influenced by magic (divination and fabrication to start with) and modern economic boom and the elimination of disease creates a massive population and technological increase. Technology adopts the scientific paradigm, which in turn is influenced by diviniation magic rendering scientific theory instantly falsifiable.
Which of course inevitably leads to a massive population and technology surge, which (following our own moldel) leads to territorial and cultural wars fuelled by technological and magical weapons of mass destruction, knocking everything into dust again.
Most fantasy worlds account for just such a 'ctaclysm' in the past. The Netherese (Faerun), Suel (Greyhawk), Istari (dragonlance) and Azlanti (Golarion) empires.
Heck, in Darksun all that is left is a giant bloody desert!
