Figured it out. I was going into the "more"options and selecting "Set Off" under "Wet Edges" (which seemingly does nothing?). Didn't notice the little toggle button to the right of the color selector. Still, it's kind of weird that switching to one brush changes a setting that stays changed when you switch back off of it.
I don't know if I should make a new post for this, but I'll include it here because it falls under this topic and also because I'm not certain whether or not it's a bug or user error on my part. I'm finding that if I switch to a DAUB watercolor brush and then back to a basic round brush, the transparent, wet edge effect of the watercolor brush carries back over to the round brush even at 100% opacity. I can't for the life of me figure out a way to get it to behave normally again.