Since your first preference was RMNLU, and if your scores match up to the criteria followed by the institute, then it is likely that you will secure a seat at RML. The seats at NLSIU also partially are considered important as well. 

The counseling (also known as the seat allotment process) is patterned in a way that students secure seats as per their preferred choice. NLSIU is a highly sought-after institute and it is the first preference for many students. 

Now, there are around 80 seats available at NLSIU including the seats for reserve category students. So, if your rank is within AIR 80~85, there is a good chance that you will secure a seat at NLSIU. 

However, if you have an AIR of around 65 and keep NLSIU as your 2nd preference then you will certainly get RMNLU and will be out of the race for NLSIU. 

You can easily drop a year in RMLNLU for NLSIU or NALSAR. The academic calendar at RMLNLU is completely different and not so tight. There are no mid-semester exams and only end-semester exams take place. 

It is not mandatory to take part in moots, debates, and mediation competitions. You can score well in your semester-end exams by studying 2 weeks before them and can easily devote time and prepare for CLAT.

Thus we can conclude that it is just a myth among people who think that they will not get time after getting admission to RMLNLU. So remove this myth from your mind and start preparing for the exam.