Well to answer your first question I usually do searchs like
"divx" followed by a filter string of "html url exe jpg zip" and a min file size of 200MB. Well when I installed the new version of phex it remembered my last search so I just ran it. It didn't automatically filter anymore so I hit apply filter and everything disappeared. Even things I thought matched this setup.

Here is what I believe is whats going on. Up until 7.1 when you put a string in the filter box it blocked all things that contain that string from appearing. Now after some experimentation I believe it only shows items that contain the filter sting.

So it used to sift and now it searches. Maybe it is a new option that you can change the functionality of this, if it is I didn't realize. Hopefully you can still sift, because I find that to be a more useful tool. Anyways if I am competely wrong about this please let me know.