You can add additional resources, we just upgraded memory and storage on all our gateways to prepare for a v14 upgrade.
If your VM does not have
hotplug enabled, then you have to reboot the VM to pick up the changes.
I do not know if the appliance model would affect if those new resources get used.
CPU usage may be limited by model, memory should be used as the new specs show either 16gb or 8gb for a v2500 depending on DRA.