Back in 2010, I tried my luck with PS2 emulation for the first time. Shadow of the Colossus ran so poorly on my PC at the time that I bought one of the last brand new PS2s (for 100 bucks, I believe), almost entirely for this game (and then I paid full price for the game, because it sold so poorly that even used copies went for 60 bucks). This game pushed the little console to its absolute limits, running at single digit frame rates in the most intense screens and forcing the fan to spin at its highest speed, so it's not just the fault of your little handheld emulation system - it wasn't very fluent on original hardware either, although still far better than on my PC. Most people played the original's faithful remaster on PS3 (different from the PS4 remake), which runs far better.

The first time I tried the system, I was shocked by the terrible image quality of the Composite cable that came with its, so I spent a rather substantial amount of money on a Component cable, which did make a noticeable difference.

Back to your emulation console: You should be able to upscale native resolution to the full screen size at least. Might look a bit blurry, but there's no performance penalty (since the same number of pixels are being rendered - they are just stretched, which even the weakest modern GPUs can do with ease) and your eyes will thank you.

By the way, there are a few Monster Hunter games for PSP, which are very easy to emulate. I've played Monster Hunter Freedom Unite both on original hardware and in PPSSPP. It looks astonishingly good and plays very well. There's also Monster Hunter Freedom, the predecessor, which I haven't played and didn't review as well. Japan got an exclusive Monster Hunter Portable 3rd, of which there's a fan-made translation, including the PS3 enhancements, that runs in PPSSPP. No idea if the enhancements work on your system, so try both the standard fan translation and the fan translation that includes PS3 assets. There's a further texture enhancement mod for the latter, but this might be pushing it (doesn't hurt to try though): https://github.com/David-vz/MonsterHunterPortable3rdHDRemake