The wav files I have, have to be 16-bit PCM. When I change it to a 16-bit PCM from a 32-bit float in Audacity, I export it, close Audacity, open the wav back up in Audacity, it’s back to a 32-bit float. Why is this?
By default Audacity works in 32 bit float format. This allows Audacity to process audio more efficiently and with greater precision (thus better sound quality).
When you import a file for editing, Audacity does not directly “load” the file, Audacity copies the data from the file into Audacity. Thus the track in Audacity is a copy of the audio data and not the original audio data. The copy is an exact copy in terms of the information, but by default it is converted to 32 bit float format.
The default export format is “16 bit (Microsoft) PCM WAV”.
If you use the default settings, then Audacity will work in 32 bit float format, the tracks will be 32 bit float format, and the export files will be 16 bit PCM WAV format.
Due to a limitation in some of the importers, some compressed formats are not converted to 32 bit float format but as 16 bit format. For best quality processing these tracks should be manually set to “32 bit float” before you start working on the tracks.
So it’s actually in 16-bit PCM format? How can I tell? As Windows doesn’t provide that information, as far as I know.
MediaInfo can give you this information, though sadly that program is now being shipped with a load of adware and other crapware.
Fortunately there is still a version available without the bundled crapware, but you need to install the version “without installer” to get it.
The version without the installer is an archive “7z” file that needs to be unpacked before use.
The “.exe” version is the installer that includes the crapware.
If you export as “WAV (Microsoft) signed 16-bit PCM” - yes. 
You don’t say what version of Windows you have (see the pink panel top of the page) but try right-click over the file in Windows Explorer, choose “Properties”, click the “Details” tab, then scroll down a bit.
Gale
For uncompressed files, you can calculate file size as a check on the format. You just have to know that there are 8 bits in a byte (and that there are 60 seconds in a minute, etc.)
The sample rate kHz is the number of samples per second (for each channel).
File Size = Sample Rate x bits per sample x number of channels x playing time,
For Example, a 1-minuite “CD compatible” WAV file is: (44,100kHz x 16bits x 2 channels x 60 seconds)/8 = 10,584,000 or about 10MB. Or, if you are mostly using 44.1kHz, 16-bit, stereo, you can remember that it takes about 10MB per minute. 32-bits will take twice as much space.