well both of those can be worn as just a face mask, that's why the eye opening is large. If you want your head uncovered just pull the top part behind your head. or if it's too warm and you want your face uncovered yuo can pull the bottom portion below your chin. I do that all the time. Most runs I'll only have the full mask up as I'm going through a snow maker.
Not sure what a turtle is, hopefully someone else will weigh in for you.