How to delete photos from iPhoto/Phots with a particular filename format?
I'm not sure either iPhoto or Photos would be keen on you deleting pictures from inside the app folder framework. 

They both expect to be 'in charge' of the editing &amp; deleting process.

I think, long term it may be better, if you want your 'originals' in a single format in each of the 3 locations to use Image Capture to do the import, to a distinct 4th location; folder on the desktop etc.

Then do your file trimming &amp; only afterwards import to iPhoto, Photos &amp; finally move the files to your Pictures folder.

Automator might be best to do the initial file cull.  

This example 'Folder Action' will throw out anything NOT containing '_highres'
Note the 'None' parameter in the filter, circled in red.
Folder Actions will trigger every time the Target folder is changed, by adding or removing content.