The basic functions of WavePad (I did not test everything) open, save, copy, paste, adjust volume, equalizer work correctly when WavePad is moved to another location.
The add-ons (for example lame encoder to enable mp3 support) are downloaded to the folder on D, so these features work too.
I hope the full, paid versions will work correctly moved to D after installation and before entering the key.
There is an option to select a work/data folder in each of NCH Suite components, but there is no option to select install location, what may be unpleasant to users.
My system drive is a SSD drive and it is only 200 GB. There is only Windows, drivers, codecs, fonts and these programs that run at startup. All other software is installed on D.
The main reasons to install third party software on a different drive is fast boot and easy-to-find any potentially unwanted files on the system drive.
The other reason, if Windows ever crashed and is reinstalled, program data and settings remain unchanged.
No need to configure every program from the beginning.
This is why I recommend adding selection of installation path to the installer (or a portable .zip that could be unpacked anywhere).