If you do not need that a cluster failover keeps up the current connections, you need no state syncronization - but usually, failover should be smooth and not disturbing any connections or services. On the other hand, load sharing needs state syncronization between the nodes as the load has to be shared. You will need a sync connection between HA cluster members anyway as the standby must learn if the active is no longer working and standby has to turn active.
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