How is 'Inbound NAT rules' different from 'Load Balancing Rules' different from each other in Azure Load Balancer v2

You would use NAT rule when you have 1 backend server or you know which backend server to get to and loadbalancing rule when you want to loadbalance to multiple backend servers.

NAT rule must be explicitly attached to a VM (or network interface) to complete the path to the target; whereas Load Balancing rule need not be. In the latter case, a VM is selected (from the back-end address pool or VMs) to complete the path to the target.