I have:
Yes, you can do this and in a lot of different ways. The most common for headless servers is by using ssh. However, it sounds like you’re talking about running a graphical desktop on a VM. If your VM is running a Windows version that supports it, RDP is what you’re after. If the VM is running a Linux desktop, try something like NoMachine.
In either case, the performance will depend more on the VM than the laptop. It would probably be worthwhile to pass through a dedicated GPU if you want to use graphic-intense apps such as Blender.
Yes, this is certainly possible. I’d personally think the easiest way to do what you are asking about is using virtual machine manager. You can easily find it using apt or your preferred method of interesting apps.
https://ubuntu.com/server/docs/virtual-machine-manager
Edit: Just to be clear, you install virt-manager on your laptop.
Doesn’t proxmox already offer a web based graphical console into its guests? Why not just use that? Does it not perform reasonably well if the user isn’t on the host locally?
Haha. Maybe - I’ve never used proxmox, so I have no clue. 
Thanks for your reply, yes, Proxmox does have a graphical console, I suppose I need to spend some time tweaking it to get the latency and resolution improved. Was just wondering if anyone had experience or has seen someone take on a project like this.
Your comments inspired me to do some research and I will be attempting to carry out some of these ideas in the near future. Thank you for providing me with some guidance, tvcvt.
Most people will use RDP to get into Windows VMs and SSH to get into unixlike VMs directly, while keeping the graphical console level access from the hypervisor around as a failsafe.
Nomachine / x2go can be similarly used for direct graphical desktop access to unixlike VMs–but again in my experience, most people don’t actually need that for unixlike VMs, which very rarely depend on the desktop the way Windows apps and services often do.