Did you watch the video? She explained in it that she was bored of the "Dwarf = Blacksmith" trope and decided to make Parsley a tiefling, which are humans with fiendish ancestry that finally decided to display itself in the otherwise normal human bloodline. (Usually. Sometimes they're their own separate race from humans, it depends on what you're playing/who you're playing with.) Tieflings are tall and tend to have red/purple skin tones. Sage was turned into an elf because she's very magic-oriented and her redesign has a more nature-y vibe, and Thyme's now some sort of faun-like creature with deer ears and antlers just because she wanted to do something different.