Yes the LANGuardian can be used as a Netflow collector. If your system license has Netflow sensor support then you can define a Netflow sensor on the LANGuardian. On your router you can then enable NetFlow sampling of the traffic and specify the LANGuardians Management IP address as the destination address for the flow.
The LANGuardian will be able to create Traffic reports such as Traffic Distribution, Top Clients and Top Servers. These reports will allow you drill down to the individual sessions and flows which make up this traffic. However as this traffic is sampled rather than the raw traffic seen for local and remote sensors full visibility to the contents is not possible. For example the Deep Packet Inspection functionality such as web traffic and MSSQL analysis will not be possible. Also the IDS will not be able to analyze this traffic as it does not see the individual packets