KobaSpeech 3 installs the 32-bit voices by default. These voices are available for 32-bit applications on your computer. (even if your operating system is 64-bit) If you want to use KobaSpeech voices in a 64-bit application, you can install this add-on. The voices will be available in your 32-bit and 64-bit applications.
To use KobaSpeech voices with NVDA you can download a driver to select the voice you want to use with NVDA.