The safest way is to purchase the official release. While SNK hasn’t released a standalone “Perfect Edition,” you can get the original The King of Fighters '97 Global Match (or similar versions) on the Google Play Store.
Key features: Online play, improved netcode, HD graphics toggle, and no malware risk.
Once you have downloaded the APK and OBB files, follow this process carefully. The game will not run if you skip the OBB data step. The safest way is to purchase the official release
Some fan-made mods (often called “Perfect Edition” or “2020 Plus”) include extra characters, moves, or balance changes. These are not official.
If you still want to try: HD graphics toggle