I believe that A7/A8X issue was only for jailbroken devices if you want to use the PSX core with dynamic recompilation.
An iPad AIr 2 should run the PSX interpreter core (does not require jailbreak) just fine.
If you’re jailbroken, install RetroArch via Cydia and:
- Go to Online Updater
- Choose Core Updater
- Choose Update Core Info Files
- Choose Update Assets
- Choose Update Overlays
- Update anything else you want (cheats, etc) but those are optional
- You should have a core called Playstation (PCSX ReARMed) [Interpreter]
- Use that core when loading PSX disk images
If you’re not jailbroken, you need to manually build the app in Xcode 7, or install it by some other means (re-signing), and download and codesign the cores yourself, and follow steps 3-8.
I assume you’re jailbroken though 