[FEA] Reevaluate Windows module for performance improvements

[mnicely]

The windows module need to be reevaluated to find areas of further performance improvements.

[awthomp]

Note: This includes similar investigations as explored in #235. Developers should be examining:

• Use of numpy over cupy for small-scale calculations like overlap size, FFT size, and other generic parameters that don't require GPU compute
• Elementwise kernels, where appropriate (either raw cupy, as denoted in the above PR, or Numba)
• Caching of FFT plans

[mnicely]

Closed by #267