Dom0 sys firewall sys whonix takes max mem

[apparatus]

Dom0 has fixed memory without balancing.
Regarding memory usage by the qubes - it’s how Xen memory ballooning works:

Why is the RAM always gone?

Not sure about increased CPU load but the memory increase you described looks like Xen memory ballooning: For example, if the Dynamic Minimum Memory was set at 512 MB and the Dynamic Maximum Memory was set at 1024 MB, this would give the VM a Dynamic Memory Range (DMR) of 512 - 1024 MB, within which it would operate. With DMC, XenServer guarantees at all times to assign each VM memory within its specified DMR. When the host server’s memory is plentiful, all running VMs will receive their Dyna…