It should still load regardless which option you choose. It's just a matter of where it loads from.
I have tested this, and WAV files saved as 32-bit float PCM load up as a single frame in TOonz. Not only that, but I noticed that TOonz WILL crash when you attempt to import 32-bit WAV files - after importing a 32bit WAV file, TOonz becomes confused, and no longer plays sounds when scrubbing the Xsheet. When I tried to drag a 16bit column past a 32bit single frame WAV column, TOonz crashes without exception.
In short, if you notice that your WAV files are loading up as a single frame in the Xsheet, it means it is a 32bit WAV file. Quite TOonz, and convert your 32bit WAV file to a 16bit version before proceeding.
To convert your 32bit WAV files to 16bit, any sound editor will suffice.
Here are the steps with Audacity:
1) download Audacity at http://www.audacityteam.org/ Either the full installation, or the zipped version which works straight out of its folder.
2) Start Audacity, and load up the offending WAV file.
3) Choose FILE-->EXPORT AUDIO
4) in the SAVE AS TYPE dropdown, select either WAV (Microsoft) signed 16-bit PCM or AIFF(Apple) signed 16-bit PCM.
5) save the file in your TOonz project. I have an audio subfolder where I put these things.