like the picture above, I have a 32C/64T AMD 3970X CPU to allocate to 4 people to use in the same time. Each person has 4 separate cores,  and the remaining 16 cores are shared. But when a vm is fully loaded, others become jammed. Is there any way to make full use of CPU resources without affecting each other?

Start by giving each VM a single matched pair of cores, starting at the high numbers, leaving all the low cores unallocated and then see how they perform. Add a pair of cores to each VM and test again. Stop adding cores when the VM's don't perform better when you add more cores. For the best VM experience leave as much power as possible for the host to emulate the other resources needed for the VMs.

You need to leave cores free for Unraid itself to use.   At the very least you want to leave core 0 (and any associated hyper-thread companion) not assigned to any VM as Unraid will be using that for its own purposes to support emulation.   I would recommend that you allocate dedicated cores from the top and work down.  I would also avoid having any cores shared between VMs if you want to avoid interactions.