Colleges in Imphal

If you are from general category then it's quite difficult to get seat in NITs or IIITs. You can try for any private college or just take drop and prepare really well to improve your rank.

In NITS and IIITS maybe not as you are from general category. Take a year drop and prepare well or try to get admission in any private college.

It could be better as you will get some good facilities and more opportunities due to the fact that you are in a government college. If you are concerned with your studies then it could be better than the state colleges. You will definitely get problems regarding infrastructure. But then you have to choose according to your priorities.

Yes, they will be accepting MAT score card of February for admission.

As from my experience, CSE in NIT Manipur would be a good option for you.
CSE is not so famous in IIIT, Sri City and also placement in IIIT is about 60-70% for CSE.
But, in NIT Manipur, placement in CSE goes up to 100%.

I think IIITs are good, but you need to do hard work.