System resources

Hi Guys, I'm getting into self hosting and have a mini nuc that I'll be using. Out of curiosity, how does it work with system resources. Eg. I have a 16 thread 64gb ram Let say for example I have the following VMs and allocated these VM1 8vcpu 16GB Ram VM2 4vcpu 8GB RAM VM3 2vcpu 8GB VM4 4vcpu 8GB

Is it good practice that the amount of threads is the maximum you are meant to allocate the VMs or does it somehow 'borrow' vcpu power if the other VMs are not being used? Would this be the same in memory?

And yes, I intend to run these VMs at the same time.

Hope anyone can enlighten me with this.