Third-party plugins don't work with every program. Generally speaking, 32-bit plugins work with 32-bit applications, and 64-bit plugins work with 64-bit applications.
However, there are also many 64-bit programs which can open 32-bit plugins.
Vegas Pro is a 64-bit program. It can open both 64-bit and 32-bit plugins.
Movie Studio and Movie Studio Platinum come in 32-bit and 64-bit versions.
The 64-bit versions only work with 64-bit plugins. You can edit projects in both versions of Movie Studio Platinum by editing at 32 bit and finalizing at 64 bit.