There are two methods to specifically target 32-bit or 64-bit OS'es in group policies.

WMI filter

• For x64 (64-bit):
  • Namespace: root\CIMv2
  • Query: SELECT * FROM Win32_Processor WHERE AddressWidth = '64'
• For x86 (32-bit):
  • Namespace: root\CIMv2
  • Query: SELECT * FROM Win32_Processor WHERE AddressWidth = '32'

Environment variable

Another method is to check the value of the %Processor_Architecture% variable:

• For x64 (64-bit): %Processor_Architecture% is AMD64
• For x86 (32-bit): %Processor_Architecture% is x86