The latest Alpha update to the AetherSX2 emulator brings about significant performance improvements. Midrange Snapdragon 860 hardware now appears to have no trouble running intensive PlayStation 2 games like Metal Gear Solid 3.
https://www.notebookcheck.net/The-AetherSX2-PlayStation-2-emulator-for-Android-has-no-trouble-running-Metal-Gear-Solid-3-at-30-FPS-on-the-Snapdragon-860-equipped-POCO-X3-Pro.596358.0.html