I am setting up a few VM's (assume VirtualBox w/ Linux). They will all be on the same PC host (assume Linux) and the intent is to have all the VM's handle separate functions (business, personal finance, and personal) and have no connection to each other through the network or otherwise. I want to set them up in a way that creates the best security as far as separation from each other and the host. The host will function only to host the VM's. I would prefer to use one VPN subscription, which has been purchased anonymously. However, if this compromises the separation of these VM's, then I would consider changing the approach.
Given this setup, which method (Bridged or NAT) would work better as far as providing the least amount of leaked information between the VM's/Host?
The plan is to set up software firewalls allowing only outgoing connections for the VM's and the host. I am still looking into whether this is the best approach (secure and user-friendly approach).