iFilter is not required for SharePoint 2013; in 2010 it allows full-text searching of PDF files.. The other two are used (respectively) for displaying the proper icon for PDF files in SharePoint, and to enable opening files directly from SharePoint (rather than having to save them first).
So, no 'issue' if you set them false, you just miss out on certain functionality/user experience.
Brian
So, no 'issue' if you set them false, you just miss out on certain functionality/user experience.
Brian