@Deadwood Al The setup impacts whether applying hours to the payroll item in question on a paycheck will reduce the available vacation or sick hours.
QB only offers two options for tracking things like sick or vacation pay which are, well, sick or vacation days.
If you plan to co-opt one of those two for PTO days instead, you'll want the PTO item to be coded as the one you chose, either sick or vacation. Doesn't really matter which one you go with.