There is my methods, how I test real performance on devices. I always use that if I doing tests for @ptr1337
What you need?
If you expect tools, special software... I will disappoint you. We want real world performance in real a scenario.
1. Select fast games, what you really know. (It mean, seriously fast - every fps drop will strongly hit your gameplay)... I recommend games where you have +200 hours. I use https://xonotic.org/ and Trackmania.
- Where fps usually went down and up.
- Aspect what's can change fps value. (Maps, number of enemies, graphics settings)
Cool tip: Remeber usuall fps value for unique weapons, vehicles parts of story - cinematic scenes)
2. Same environment for device (Avoid to interferences from thermal throttling)
- Same or similar temperature at your room.
- Same place for device (More important than room temp) - airflow is differently if you change place where you use device.
3. Use only 3 scenario for testing, you can't correctly memorize more.
- Small, medium and large map where you will observe fps value. Don't use more maps!
4. Hard core conditions.
- Set your game on graphical settings where you have 30fps... everything smooth for you, if fps went up or down... you know immediately. (Mmm game is better or worse), you can't see so much changes if you play on 60+ fps.
Apart from me... I have nystagmus - rapid involuntary movements of the eyes. Smooth movements start for me around 50 fps.
- Play with sniper rifle... lower or unstable fps is hell for this.