Hey In the backend on IIS im guesing you have Web Platform Installer Working? (WPI can install both versions of PHP) And PHP Manager? you should be able to install/add both x86 and x64 PHP versions and have them available for your websites.
That is working great and we have been running it like this for a long time.
The problem is in the user GUI in MSPC.
On the website and Extensions it just display 2 “PHP 7.0.9” The client can’t tell if it is x86 or x64.