What profiling steps and optimizations fix CPU-bound FPS drops on Android Unity?

[MadisonET]

I'm a solo developer working on a 2D pixel art game for mobile, and I'm hitting serious performance issues on older Android devices during scenes with multiple particle effects and enemy AI. I'm using Unity and have done basic mobile game optimization like reducing draw calls and using sprite atlases, but the frame rate still drops unpredictably. What are the most effective profiling steps and specific optimizations for CPU-bound logic and particle systems in Unity to maintain a stable 60fps across a wider range of hardware?