PPSSPP options explained

[LunaMoo]

Setting render res to auto aka your device resolution will set it to x4, if you can't see a difference on such a small screen, just go with x2 and it will be 4 times more efficient than x4.

Take note that x1 while might look less sharp will also be free of artifacts that happen with increased rendering res(since PSP games were NOT designed to run at higher res and this is kind of a hack) and in some games badly affected by those it might still be a nicer choice especially if the game is fully 2D and doesn't scale with rendering res at all.(but while using x1 I'd recommend also switching "Screen scaling filter" to nearest, otherwise it will blurr the image a lot by trying to stretch x1 to x4)