Here is my take...
If it is going to be a dedicated set up go with the Rio Nymph line or 000. The main reason is sag between the guides. If you go with a DT or WF you will get some major sag. The sag will cause you problems with always trying to pull the leader back through the guides. Even though my leader set up is close to 20ft, my fly line is at least always in my guides. Usually it is outside of the tip (Just the tip). If you are trying to nymph a seam 20-30 feet away, which is normal, that DT or WF will sag outside of the tip and you won't have a direct connection to the flies. It will want to fall directly below the tip of the rod, where a lighter line will basically be in direct connection with your leader. Another benefit is the feel in your hands. The smaller diameter line you will be able to handle better.
The Rio Nymph can be flipped just as the DT. I have used mine for 2 seasons and just flipped it. I will probably get at least another season maybe 2 on it.
Btw, how I nymph, mostly upstream, my first cast the fly line is almost always on the water. Slowly stripping it in to get that direct connection with the flies.
Feel free to message me if you have any other questions.