You can dual boot with 32 bit on one partition and 64 bit on the other. Why you would want to do so however is beyond me. Seems a total waste of time and hard drive space together with a problem of getting hardware drivers for bvoth versions. My advice is forget it unless you want an emergency system but then you could have two x 32 bit or two x 64 bit systems.
HTC U12 Plus review: Hands-on