Which institution is better for CS: Thapar University, LNMIIT, or Nirma University?

One of my friends studied at LNMIIT, so I might be able to provide you some information about it.

CS at Thapar is combined with other courses, some of which are worthy while others are not. You have to choose the course which you are interested in. Depending on that you can opt for the college, be it Thapar or LNMIIT.

The infrastructure and facilities at LNMIIT are really good. Faculty members are enthusiastic about both academics and extracurriculars. They will guide you through every step. LNMIIT has a great coding culture. Also, you will have cooperative seniors.

I am not well aware of Thapar, I can only say that the campus and course curriculum is more or less similar to LNMIIT, unlike Nirma which can be a bit different. So finally I will suggest you go for LNMIIT. Make Thapar your second choice as the quality of the branch varies. Lastly opt for Nirma if both do not work out.