All RUT devices can be accessed remotely via WebUI or SSH. First you should enable “Remote HTTP access” or “Remote SSH access” (WebUI -> System -> Administration -> Access Control). Be careful and don’t use weak password.
If you have static public IP, you will be able to access your device. You don’t need VPN for this.
If you have dynamic public IP, you should use Dynamic DNS, RMS or VPN.
If you have private (public shared) IP, you should use RMS or VPN.
More details about public and private IP you can find here: