Is National Institute of Electronics and Information Technology agartala good university?

First of all it's not an university. It's an Institute affiliated with Tripura University. You can say it's a decent institute. In my opinion, if you have choices to go to NIT then don't choose this institute. Just  go for NIT.

It is a decent University. However, considering the fact that NITs have State quota, and that the results of the state in JEE Mains is not good, the quality of Education is a bit hampered. Plus, the corruption is prevalent everywhere. So, consider your position and all the facts before joining.