Greetings!
Indeed, Dragons are of course an iconic and terrifying creature within a campaign world. In my own campaign world, I generally use three different kinds of dragons; Linnorms--a kind of Nordic style dragon, usually at least semi-intelligent, and physically powerful, but not generally known as spellcasters. Then, there are a kind of standard Drake--basically similar in statistics and abilities as Linnorms, but having a different appearance. Then, there are the primordial Dragons, which have magical powers, spellcasting abilities, in addition to their impressive and awe-inspiring physical abilities, much like a quasi-natural disaster striking an area, like a flood, hurricane, or a volcano blasting off in eruption. I like having a variety of dragons in the campaign. It is always nice having some super-epic monstrosity as an encounter in an great, heroic adventure, for higher-level characters. That kind of encounter gets armies marching, kings involved, with economy-swaying influences, as well as having significant impact on the campaign region as a whole. However, especially for lower-level character parties, it is also great fun to have lower-level dragons living in various dungeons and lairs across the land, serving as low-to-mid-tier opponents, as well as potential allies and friends, in an environment where fighting them and defeating them serves as a huge embellishment of the Character's reputations, infusion of wealth and treasures, as well as acting as potentially very important story or plot points during the campaign--all while not necessarily having some huge impact on the region's economy or political environment as a whole.
Semper Fidelis,
SHARK