PTP for photo transfer not working on my S6 edge
You can use Android File Transfer to browse your device in MTP mode. All pictures are normally saved in Phone/Camera/DCIM/ or SDCARD/Camera/DCIM/, by date. You can drag and drop the files to your mac. It essentially works like a Finder window. This way only the files you choose are transferred and at MTP speeds instead of PTP.

As for PTP not working, I'm assuming you have PTP selected, and screen unlocked when you try to open iPhoto?