the folder in your second screenshot is full of .aax plugins. ALK2 only supports AU and VST plugins, not AAX ones. My guess is that you are searching for the AU version of the BIAS FX and that you will find it if you add the following plugin folder: /Library/Audio/Plug-Ins/Components/
This is where AU plugins are usually stored on OS X.
With regards to your second question - currently ALK2 lists all the supported plugins (VST and AU) found in the plugin directories. There is no filter yet that would allow you to only see one or the other kind. You can of course always remove the VSTs folder or the AU folder and then you will have only those in the list.