If you build as 32-bit, your payload(s) must be 32-bit. If you build as 64-bit, your payload(s) must be 64-bit.
GUI applications can only be injected into GUI applications, and console applications into console applications.
Auto-Inject methods are recommended, as they will automatically detect if the machine is 32-bit or 64-bit, as well as the executable architecture to make sure the path is right for the injection.
When you build, both 32-bit and 64-bit builds are included in the zip file.