Hi,
1.
8-Way vCPU for Standard license
32-Way vCPU for Enteprise license
64-Way vCPU for Enterprise Plus license
2.
You can create as many groups as you like in your directory ( LDAP / ADS / Local ) and use it to configure permissions.
3.
Using Accounts from external directory like ADS is much more common, but the local accounts on the ESXi hosts are SHA512 hashed.
Regards