Unstable FPS while playing Metro Exodus - Enhanced Edition

Update:

I installed and played Cyberpunk 2077 today and used the default graphic settings of ray tracing ultra at 1080 P, the fps is around 50 - 58 avg, not too bad actually. The GPU power being used is over 110 watts. So it proves the GPU is ok, so I am pretty sure it's the Metro exodus enhanced edition somehow not utilizing the full power of the GPU.