On IPfire you can install the Zabbix Agent, to monitor your IPFire instance. You will need to have a separate (monitoring) server running Zabbix Server. You cannot install Zabbix server on IPFire itself.
Please also check out this post for a few starting points and interesting links for getting started with Zabbix.
Once your IPFire instance is monitored by a Zabbix server using my IPFire template, OpenVPN clients are indeed monitored in ‘realtime’ (every one minute). You will be able to see the connection state and amount of data that is being transferred.
IPsec VPN is currently not yet implemented in the template.