What availability mode does vCenter HA provide?

Active-Standby is not the correct VMware terminology for vCenter HA - the correct term is Active-Passive, and the distinction matters because the passive node is continuously synchronized with the active node, not simply powered off on standby.

Load-balanced mode is not a vCenter HA option - vCenter HA does not distribute vCenter Server workloads across multiple nodes simultaneously.

vCenter HA is architected with three nodes - an Active node, a Passive node, and a Witness node. All vCenter Server services run exclusively on the Active node, and if that node fails, the Passive node automatically assumes control. The Witness node monitors both nodes and casts the deciding vote during network partition events to prevent split-brain conditions.

Active-Active is not supported by vCenter HA - only one node runs vCenter Server services at any given time, making simultaneous active operation across multiple nodes impossible in this architecture.