Should I play the Nizmo Indian Defense?


I think you should play whatever you feel like and try out as many of the main opening systems as possible to gain overall chess experience. Nimzo-Indian certainly has less variety and complexity than all the possible Sicilian variations. Most of blacks plans are quite straightforward.
Playing the Nimzo-Indian at 1200 is fine. Just remember you also need the Bogo-Indian (not too happy recommending the Queen's Indian).

I think you should play whatever you feel like and try out as many of the main opening systems as possible to gain overall chess experience. Nimzo-Indian certainly has less variety and complexity than all the possible Sicilian variations. Most of blacks plans are quite straightforward.
Actually, this is completely incorrect. The Nimzo-Indian probably has more pawn structures to know than any other opening. You've got the blocked center (i.e. Hubner), IQP center (i.e. certain 4.e3 lines), fluid centers (i.e. certain 4.f3 lines and certain lines of the Saemisch), and a number of others, including the Carlsbad Pawn Structure.
The QGD leads to a more consistent pawn structure, with basically two main ones to deal with. Those where Black takes on c4, and the Carlsbad Structure that comes from the exchange.

Considering your ratings, and the only things you play are blitz, and bullet. You need to ask yourself the following:
1. How am i going to learn an opening when all i'm playing is fast time controls? How do you plan on implementing what you're trying to learn, when you're moving fast?
2. Will learning a new opening help me to resolve the following issues in my game:
Not following opening principles.
Missing simple tactics.
Not hanging material.

Indeed. In my opinion, it's a solid defense. Thing is, you also have to learn the Queen's Indian too (QID). But yeah, they share similar concepts. My thing is always play over Master games of past and current exponents. Playing against an engine is always cool. Keep in mind first and foremost: defense is all about equalizing first; " counter-punching", prophylaxis, negating...so on. Anyways, I recommend it. Best wishes.
not too happy recommending the Queen's Indian.
Why not?
The Queen's Indian is nice for white. Of course if black is a strong player then he can equalise, but at the 1200 level and also above I think it's giving white too much action in the centre. The Bogo-Indian has a nice plan of d6 and e5 to take some control in the central dark squares.