If you are having trouble with DS Video outside your network, using Plex will not help.
If you have a slow connection nothing will help except changing ISP perhaps.
In your router settings, create a Port Forward rule that uses TCP, port 32400 and point it towards your NAS IP address.
It is also a good idea to give your NAS a static IP address or if your router supports it, use DHCP Reservation.
In Plex settings > server > remote access > show advanced, enable ‘Manually specify public port’ and leave it set to 32400. Click on Apply and then click on Save Changes.
When you are outside of your home, go to https://plex.tv and sign in there, if not already. Then click on Launch. Plex/Web (remote version) will open and you can access your Plex server at home from there.
If you have a Plex app on your mobile device, simply use that instead.
To help with transcoding, you need to have the following:
- A valid Plex Pass
- The 64 bit version of Plex installed
- Hardware Acceleration enabled in Plex settings > server > transcoder.
That will help when Plex needs to transcode a file to a lower bitrate to send across the network.