I usually enable ‘enhanced resolution speed’ in core options when I enable enhanced resolution. Try it, perhaps it’ll give you better performance. I think the pcsx core runs great on the iPhone 4s, which shares the same internals as the iPad 2, except that the 4s is clocked around 800mhz, while the iPad 2 is higher at 1ghz. When it came to playing fast action type ps1 games on the iPhone 4s, enhanced resolution was a no go and just required too much out of the 4s that it didn’t really have to offer. So I kept that option off, though I’m surprised that the iPad 2 is giving some trouble as well, seeing as it’s clocked higher and all. I had the iPad 2 once, though that was way before retroarch came into the picture. I still think it’s a pretty capable device, same goes for the 4s. If you want to stick to using an A5 device, your best bet is stick to stock settings (instead of using enhanced resolutions or filters). If you can find a filter (such as NTSC gauss pass) that doesn’t take too much from your device, it could help give you that old school retro look. In the end though, if you want something that will give you better performance all while being able to use more shaders (though not by too much, I had an iPad 4 as well-A6 device) and enhanced resolutions, the iPhone 5 will allow you to do that, though on a much much smaller screen.