Answer: Muggle/Wizarding capitalization
immortalje wants to know: In the example "the Wizarding/Muggle world," what words should be capitalized?
Fortunately, Harry Potter is a book fandom, so we have a written source.
As much as J.K. Rowling's universe overlaps with our own, her books are still fantasy books and, as all fantasy authors do, she created the rules for the bits she made up. So, diving into Rowling's text, I see that Dumbledore wields a Put-Outer to extinguish lights, Floos are distinguishable from ordinary flues, and a wizard or witch might be a Metamorphmagus. Yet brooms are still brooms, even if they fly, though their make might be Cleansweep or Firebolt.
For our reader's particular question, Rowling uses "wizarding world" and "Muggle world." Follow the canon author's precedent.
Fortunately, Harry Potter is a book fandom, so we have a written source.
As much as J.K. Rowling's universe overlaps with our own, her books are still fantasy books and, as all fantasy authors do, she created the rules for the bits she made up. So, diving into Rowling's text, I see that Dumbledore wields a Put-Outer to extinguish lights, Floos are distinguishable from ordinary flues, and a wizard or witch might be a Metamorphmagus. Yet brooms are still brooms, even if they fly, though their make might be Cleansweep or Firebolt.
For our reader's particular question, Rowling uses "wizarding world" and "Muggle world." Follow the canon author's precedent.