I'm a beginner newt owner so my experiences are pretty limited but hopefully helpful. I tried keeping ricefish with my alpine newts when I first got them. I ran into the double issue of the newts not wanting to be in the water and then once they did go in, of at least one of the newts partially eating one of the fish. These were juvenile newts as well less then a year old. Some people have better luck with fish in their tanks while others say its generally a bad idea. If you do decide to go for it you will need 1) a coldwater fish, 2) a very peaceful fish. The danger being the fish attacking the newt or competing with the newt for food. I keep shrimp (both amano and neocaridina) with my newts and they seem a much better match.
The biggest challenge most newt owners (including myself run into is temperature. The newts like it cold, 70 degrees is kind of the top end with many wanting to be in the 60s (or possibly colder). Your tank will need a screened lid to keep the newts in anyway so putting a fan up there blowing across the surface will help to lower the temperature.
You definitely need to cycle the tank before the newts go in, and unless doing a fish in cycle, before the fish as well.
As a final word I will say that eastern newts are all wild caught in the states. If that bothers you, you should consider other newts. I went alpine because 1) I think they look pretty cool, and 2) they are pretty widely available in the hobby, and 3) they are all captive bred in the states.
Hopefully this is helpful.