Just a note: 2X is the default resolution for PPSSPP in the source code. I built it from source recently, and that's the resolution that comes up the first time it's booted.

So, this is not a Retropie specific problem. It's the default for the application. Whether Retropie wants to override the default I'm not sure. Personally I think that 2X with frame skip is way more enjoyable than 1X without frame skip. But that is of course personal preference.

Also, with the Raspberry Pi 5 the default of 2X should run great. Though I won't know until my board gets here.

Cheers.