Once a vCenter Server has been converted to a vSphere+ and/or vSAN+ subscription, entitlements and usage for both vCenter Server and their respective ESXi hosts is all managed through the use of VMware Cloud Console as shared in this recent blog post.
If you are logged into your vCenter Server, how do you check whether it is using a vSphere+ / vSAN+ subscription or not?
Using the vSphere UI, you will see a new Subscription entry on the left hand side when selecting the vCenter Server inventory under Configure->Settings->Subscription which will indicate that this vCenter Server is using vSphere+ / vSAN+ subscription. You will also find a similiar UI entry for each ESXi host that is managed by that vCenter Server, but this is actually irrelevant because all ESXi hosts are automatically subscribed once you have converted your vCenter Server to subscription.
How about checking whether a vCenter Server is using a subscription via Automation?