What type of VPN? Generally VPN clients don't need static IPs, unless they are used for LAN access, in which case you just specify the LAN IP. If the VPN firewall rules allow only certain IPs to connect to the server, at the moment I can't think of a way to circumvent this without public static IPs. (Unless I'm missing something here.)
Not sure what you mean by "RMS is for management "only". To sum up, it can be used for:
- monitoring devices (from basic statuses like connection state, modem temperature, uptime, etc. to more advanced things like tracking the GPS position or making data usage charts);
- both mass and single device configuration;
- reaching the Web and CLI interfaces of your devices;
- setting up alarms and reports;
- upgrading firmware of single of multiple devices at a time.
As I've mentioned earlier, all devices receive a free month-long license first time they are added to RMS. So if you'd wish to try it out yourself, you can create an account here, add one device and see if it's what you need. First start instruction can be seen in this video.