Yes, you can! Mobile GPUs are limited in performance, so overclocking can really help improve frame rate or rendering performance.

Does overclocking GPU increase FPS?

Overclocking a GPU increases the base clock and frequency. So primarily, at the same quality, it will increase only FPS...

Is overclocking GPU safe long term?

Reputable. As long as you keep the temps in the recommended range, GPU or CPU, you *should* be fine (any overclocking entails some risk).