How to evaluate CUDA performance?

I programmed CUDA kernel my own. Compare to CPU code, my kernel code is 10 times faster than CPUs.

But I have question with my experiments.

Does my program fully be optimized using all GPU cores, proper shared memory use, adequate register count, enough occupancy?

How can I evaluate my kernel code's performance?

How can I calcuate CUDA's maximum throughput theoretically?

Am I right that compare between CPU's GFLOPS and GPU's GFLOPS and GFLOPS rate is transparent theoretical performance of them?

Thanks in advance.