And 1/2c is a pretty middle of the road escape velocity for a neutron star.
The lightest known neutron star, at 1.4 solar masses has an escape velocity of right around 1/4c, while the heaviest at 2.35 solar masses is 3/4c.
All of which assumes the neutron star isn’t spinning. Equatorial bulging caused by the rotation reduces the escape velocity at the equator relative to the poles and depending on whether or not you launch with the direction of the rotation you might be able to subtract the rotational velocity from your escape velocity.
As an example, in the case of that 2.35 solar mass neutron star, it has a rotational velocity of approximately 0.24c. So of you launch with the rotation you get an escape velocity of 0.5c, whereas if you launch against it you’re looking at more like 0.98c.
Might be a bit late on this, but ProxMox doesn’t really handle assigning threads to the e/p cores. That’s handled by the kernel and as long you’re running kernel version 6.1 or greater you should be good on that front.
If you really need to, you can also pin specific VMs to specific cores. So that if you’ve got something that always needs the performance it can always run on the p-cores and things that aren’t as demanding can always run on e-cores.
That said, especially if you’re over provisioning, it’s probably better to let the scheduler in the kernel handle thread assignments.