I know a few things about LNMIIT since I have few friends there. It is a public-private non-profitable college, located in Rajasthan. From what I heard from my friends, I will not recommend choosing this institute. 

• The main problem of this institute is the administration. There have been many misconducts by the management, in recent years.
• Scoring marks in college is very hard as the teachers usually give D and F grades to their students which makes their GPA < 6 and hence making it difficult for them to sit in the placements.
• There is nothing like supplementary exams which is common practice in IITs and NITs.

If you want to build upon your career, don’t choose LNMIIT. Mostly, half of the batch fails in the exams.

Finally, life is tough at LNMIIT, so don’t go for it. Look for other options.

IIIT Delhi is clearly the best choice out of the three options especially if we are talking about CSE. Your preference order should be the following.

IIIT Delhi (Indraprastha) > Thapar University > LNMIIT Jaipur

Cutoff: (IIIT D > Thapar University)

The quality of the students also has an effect on how the college performs and also in its rankings. The cutoff for CSE at IIIT Delhi is around 200-225+. Thapar University admits students with JEE Mains marks more than 170 for students’ outside Punjab and 150 marks for students from Punjab. The cutoff indicates IIIT D offers a better peer group. 

Placements: 

• In terms of placements and internships, IIIT Delhi tops the list. The avg. package for the CSE branch in IIIT Delhi is around 15 lakhs per annum. 
• Overall avg package in Thapar University is around 8 lakhs per annum and for CSE Branch is around 10 lakhs per annum with a placement rate of 94 percent. 
• In LNMIIT Jaipur the avg packages are around 6 lakhs per annum. 

Thpar has a great coding culture. However, based on student crowd, placements, etc. the best option among the given choices is IIITD.

I have friends at both IIIT Guwahati and LNMIIT and based on what I heard from them, I will recommend that you choose LNMIIT. Here are the reasons why.

• The campus life over there at LNMIIT was far better than any other college. In case you are someone from the North, you'll have difficulties adjusting to Guwahati. There isn't anything to find here be it a good social life, or cafes to chill at.
• In terms of placements, LNMIIT has so much to offer. 
• In recent years it has made tremendous strides, some even claim that it has become better than Thapar University.

Being said that you can go to IIIT Guwahati if the course fee is a matter of concern for you. It is better than taking student loans for LNMIIT. IIIT Guwahati is also a viable option. 

I have a few friends from both Thapar University and LNM-IIT Jaipur and based on the reviews I got from them, I will say LNMIIT Jaipur will be a better option. Here are the reasons why.

• Batch Strength: The total number of students at LNMIIT is less than 600, so the competition will be less in this college. 
• Placements: The placement scenario of this college is excellent. Top companies like Microsoft, Amazon, Oyo, Uber visit the campus for placements. Samsung is a mass recruiter in this college and has offered packages of more than 13 lakhs per annum. According to the recent placement highlights the average and highest CTC offered to the students are 12 LPA and 58 LPA respectively. Students also perform well in off-campus placements. 
• Workshops: There are various kinds of workshops such as GSoC, mun, and many cultural and technical fests organized in the college. 
• Reservations: There are no reservations or state quotas for admission. 
• Coding Culture: The campus has a good coding culture. 

Hence, LNMIIT is a very good place to pursue CSE, but a college is just a medium and it completely depends on how you can utilize your 4 years in the college. Your success will depend on your hard work and efforts.