I am currently testing some different scenarios with ESXi and pfSense.
Allocated ESxi: 1 CPU. Almost 100% in use in pfsense GUI. 50% on the host.
Allocated ESxi: 2 CPU. 48-55% in use in pfsense GUI. 52-55% on the host.
Allocated ESxi: 4 CPU. 24-27% in use in pfsense GUI. 28-30% on the host.