DF starts off best described IMO as what Sid Meier's Alpha Centauri described as "Frontier Economics": there is ownership, but survival needs trump it. Natural resources are free for the taking, raw materials are generally considered a common good, but finished materials are frequently owned. Additionally, while theoretically any dwarf can do any job, in practice it is more efficient to allow specialties to develop.
As the nobility kicks in, a DF fort transitions toward a direction that is not quite either Feudalism or Monarchy, but looks similar. The fundamental two-way contracts of early feudalism seem to be missing or skipped. Given the DF setting, the logical conclusion is that the DF mountainhome has transitioned into a late-period faux-feudal monarchy (or even monarchy-themed crony dictatorship) already; your fort isn't "naturally" evolving political structure, but instead is having the structure of the mountainhome thrust upon it once it becomes interesting or important enough to pay attention to.
Seeing how large and prosperous your fort can get while maintaining the frontier economics is a reasonable challenge goal; in the current version it may require some careful planning due to the inheritance rules. (Shutting yourself off from the outside is no longer a reliable way to avoid nobles without some attention to world parameters, in particular.)