Every genealogy group I’ve ever participated in gets regular posts from people who are hung up on the idea that names have one correct spelling. They don’t understand that until very recently spelling was an art form. If you look at original documents, you’ll often find the same individual’s name spelled multiple ways. Sometimes you’ll see family members who spell their surname differently.
I’ve been working on a one name study for years, and this is the list of name variants I’ve found in the wild. Some of them are make more sense than others, but none of them are wrong. So I wouldn’t spend too much time worrying about whether or not Runkle and Runkel are the same name. They are.