Active recipients is basically a count of the number of messages waiting in the delivery queue. This is not the same as the number of connections. Connections out basically shows you the number of "current" connections on progress to that destination host. Delivered recipients is the number of successful deliveries to that destination host since the last reboot of the appliance. Soft bounces are messages that got bounced by the recipient domain but have not expired and are waiting for a retry. This retry pattern typically follows, attempt, if the attempt fails, try again in 3 min, then again in 3 min, then 3 hours , then 3 days. If after 3 days we can not deliver the message to the destination the message will expire and this is what is known as a hard bounce. At that point the sender is notified their message failed. Addtionally you can get specifics on a host using the hoststatus command from the CLI.
You can find more details on tophost in the online users guide. While in the GUI if you go to the upper right hand corner and select help, then online help this brings up help for the current section your in. You can also search the help using the search panel on your left. If you search for tophosts you can find additional information. You may also want to explore bounce profiles as well.