When multiple VMs share a storage device on the same host, where does the data actually travel?

I am trying to figure out the optimal way to share storage with multiple VMs on the same box. I am aware of a range of options: NFS, iSCSI, fibrechannel, bridged, etc, but I am unclear how they fit together or are mutually exclusive.

Here are a few statments of what I understand to be true based on what I have read so far, but an not certain of. If someone could either affirm or correct my understanding, that would be great. At this time I am thinking about using Proxmox (KVM+ZFS), but if other hypervisors have important differences with respect to these statements, please do explain.

True or False?:

1. For sharing storage devices between VMs on the same host, I can used bridged networking to maximize speed.

2. With bridged networking, no physical network hardware is being used, instead the CPU is acting as a virtual NIC, which is faster because the limit is the speed of the system bus, rather than of ethernet/fibrechannel etc.

3. For the reason stated above, there is no benefit to using something fancy like fibrechannel to share storage with VMs, except the elimination of a small amount of CPU overhead. Using a fibrechannel card would be needlessly creating an extra step for VM interaction with the hosted storage.

4. The speed and complexity of setup of iSCSI vs NFS is something that varies a lot between hypervisors, so this choice should be made once I have everything else decided.