You can certainly do it any way you like, it should function fine either way. Just know that cameras are notoriously insecure, so by opening up ports, you expose your entire infrastructure. There are still pretty severe ONVIF vulnerabilities in lots of cameras.
The VPN route is actually easier than managing all that port forwarding, anyway. It might be new to you, and what you are already familiar with certainly seems easier, but it really isn't.
On your 68u, just go to VPN and then the VPN Server tab. Turn Server 1 on, Apply and press the Export button.
Then put that file you exported on your phone and install the OpenVPN client on your phone. If it is an Android, go here:
https://play.google.com/store/apps/details?id=net.openvpn.openvpn
Then run the client you just installed, hit the + and import the config file you exported from your router.
Now you have a much more secure way of accessing your entire home network from your phone.
You can have TinyCam scan the IP addresses of your cameras (use Advanced Scan) and it will identify and configure them for you.
ThisI is from memory and if I left out any steps, hopefully someone will say something, but this should do it. It is about a million times safer than opening up your firewall and exposing cameras.