Follow the following steps to add specific user and group access to a single ESXi host:

1. Configure a single group, be it AD (remote) or Local.
2. Add user to the above group.
3. Login to the VCSA (vSphere Client).
4. Select the ESXi host.
5.  Click on the Permissions tab.
6. Click on the + icon.  You will be in the Add Permission | host01.domain.abc popup.
7. Select the domain.
8. Select the group.  Start typing so the filter can locate your group.
9. Select the role to apply.  ( Roles can be defined by the Administrator )
10. Propagate to all children, if you wish to do so.
11. Test!

HTH,