Does pfSense support 64 bit systems
Yes. All supported releases of pfSense are 64-bit capable when using pfSense images labeled with "amd64" for both Intel and AMD CPUs using the AMD64 architecture, also known as x86-64.
32-bit images and support (i386) are deprecated with the pfSense 2.4-RELEASE and from it 64-bit systems are be supported exclusively.
32-bit images can run on 64-bit hardware, but this is not recommended and should not be done. If the hardware is 64-bit capable, run 64-bit images.