Varenyky are on the size side you prefer them to be. Being small or big doesn’t stop them from being varenyky.
there’s no “usually”, in every household every person makes it as they please at each preparation iteration, according to the size of their hands, capabilities, mood, and especially filling. you do cherry for kids - make them smaller, one cherry inside. oh, today your kid wants them full of cherry juice hinkali-style, voila, enormous ones, and the juice drips. same thing with borshch, or other “staples” of Ukrainian cuisine. there are no rules, only slight directions. do as you please.