Is Windows 64 bits supported for end users?

Yes, but if their application include any third-party DLLs those DLLs also need to support 64-bit.  If it is pure PB application and no third-party DLLs are used then automatically Appeon creates both 32-bit and 64-bit versions, and will serve the correct version based on if user has 32-bit or 64-bit IE browser.