Grenadiers were picked for their imposing physical characteristics, but seeing as commissions were often bought or hereditary how did this relate to commissioned officers and NCOs? Were there exceptions to the rule, or did everyone in a grenadier company/battalion have to fit into the category?
Edit: I say early 19th century rather than simply 19th century as I don't know enough about military organisation post Napoleonic wars to make the question applicable.
Within the French military, the height requirement was not an absolute rule. There's a story of Marshal Davout, known for being a strict but fair commander that did things by the book, telling a potential applicant to the Imperial Guard that he should place a pack of cards in his shoes to make in just tall enough to gain entry.
As for NCOs, many rose up the ranks from the line, so generally they would fit the height requirement. However officers would be assigned and transferred in and out as needed, more on availability than height requirements.
While the British are famous for their purchased ranks, it was a common practice in many armies, certainly the Austrian army. Here, the person purchasing the rank didn't have any sort of requirement based on the unit itself, many German officers ended up commanding Hungarians, Italians, or Bohemians. So it ends up happening more on chance and purchase than requirement.