Look for .CHD files. They combine the small size of 7z with the "playability" of an ISO. You don't extract a .CHD; you load it directly into the emulator.
Widely considered the best for performance and compatibility. ps2+iso+highly+compressed+for+android+verified
The preferred choice for Android. It is a lossless format that significantly reduces size without losing data, and it is natively supported by emulators. Look for
In AetherSX2, set "EE Cycle Skip" to 1 or 2 to help lower-end CPUs keep up. ps2+iso+highly+compressed+for+android+verified