I usually only produce plump helmets in one of my smaller farm plots, and then only in winter (other seasons go to quarry bushes). My main food supply is quarry bush leaf roasts, often flavored with the meat or organs of whatever carnivorous creatures I can get my hands on. So yes, at least one person makes forts that consume foods other than plump helmets. When I play modded games where my people aren't alcohol-dependent, I'll usually try to make my fort eat nothing but meat and no have farms at all! More challenging initially and takes more micromanagement, but that's all just more fun.
To feed and booze my dwarves, I typically have 3 farm plots, one large at about 20-25 tiles and 2 small at about 8-15. One dwarf is a planter and does nothing else, everyone harvests. The large plot produces sweet pods, pig tails, and cave wheat, depending on the season; these are used for booze. One of the smaller plots produces dimple cups and pig tails, with the products mostly going to the textile industry. The other smaller plot produces quarry bushes 3 seasons a year and plump helmets over the winter, and is my primary food supply. If necessary, I'll switch plump helmets on the large plot's winter schedule, which normally lies fallow. Once my farmer hits legendary, they can easily keep all ~40 plot tiles full, and produces ample amounts for even very large forts.
My stills tend to primarily make dwarven ale, since pig tails are most abundant, but dwarven wine is also common since plump helmets produce so fast. I avoid milling sugar or flour when I can, though it's somewhat difficult as you can't restrict that as easily as I'd like, so rum and beer is also readily available. As far as food goes, quarry bushes processed into leaves then cooked into roasts satisfies gustatory needs, though I'll usually slaughter the occasional animal and cook it into my roasts as well.
Overall, eating just plump helmets is for newbies; it's easy to feed and booze a fort on the shrooms, but once you're experienced enough, it's unnecessary. If you want practice with food management, you might try modding the game so that you're controlling a CARNIVOROUS race; being unable to use the mostly fire-and-forget farming system is good training. Also, removing ALCOHOL_DEPENDENT so you can drink water without penalty is helpful, as it means you can drop out farming altogether.