If “32-bit Floating Point” is listed, that means it properly supports the 32-bit color editing mode available in Vegas as well as the default 8-bit mode.
GPU indicates whether that effect is GPU accelerated.
No. If you had the 32-bit version of Vegas Pro 10 installed, it would install the 32-bit version of the plugin. If you had the 64-bit version of Vegas Pro 10, it would install the 64-bit version.
If it was an installer for Vegas Pro 10, it would have included both 32-bit and 64-bit versions. However, if it was for Movie Studio 10, it would have been only 32-bit.