Real compression usually caps out at about 30-60% of the original size.
A high-level open-source emulator that is easier to set up but has lower game compatibility compared to AetherSX2. How to Get and Run Highly Compressed PS2 Games ps2+iso+highly+compressed+for+android+verified
In AetherSX2, set "EE Cycle Skip" to 1 or 2 to help lower-end CPUs keep up. Real compression usually caps out at about 30-60%