Spacing between gaussian windows for STFT
usually the overlap has more clear meaning when used with a complementary window such as the Hann window.  a complementary window is such that the tails of all overlapping window functions add to 1.  $$ \sum\limits_{k=-\infty}^{+\infty} w(t-kT_{\text{hop}}) \ = \ 1$$  that cannot be the case for overlapping gaussian window functions.

if your STFT is just for analysis, not synthesis or reconstruction, then complementary windows do not usually matter.  then the issue is more about frequency resolution (which determines how wide the window is) and the STFT frame hop distance.