Difference between Port translation, Address translation and SNAT?

Port and address translation are for destination address and port. In a standard VIP configuration, with port and address translation enabled, when packets from the client arrive at the VIP, the destination address and port are changed from the VIP's address and port to the load balanced server's address and port. You can obviously enable/disable each individually for different effects. When you create a wildcard VIP (0.0.0.0/0:0), the port and address translation settings should be automatically disabled. This would be used in scenarios like firewall load balancing (inbound) or forward proxy (outbound) where you definitely don't want the original address and port altered.

SNAT is for changing the SOURCE address. Without SNAT, packets from the client arriving at the VIP retain the client's true source address. SNAT is then important if the downstream server knows how to route back to that address directly (not back through the F5). SNAT will change the client source to an address controlled by the F5 to essentially force return traffic back through the proxy.