The IP Pool don't need to be on the same network of your vCenter server but you will need open some ports between your vCOPs and vCenter Server... and about disk requirements, check the quote below from vCOPs 5.8.2 release notes:
Balanced Profile
- Maximum number of objects: 12K, 2.2 million metrics
- Memory
- Analytics VM: 21GB
- UI VM: 26GB
- vCPU
- Analytics VM: 8 vCPU
- UI VM: 8 vCPU
Full Profile
- Maximum number of objects: 12K, 5 million metrics
- Memory
- Analytics VM: 63GB
- UI VM: 26GB
- vCPU
- Analytics VM: 24 vCPU
- UI VM: 16 vCPU