Greetings!

Congratulations! I'll start off with BITS Pilani dual degree chemistry, so when you take admission as a dual degree student in BITS your branch of B.Tech is determined on the basis of your performance in first year, so after you complete your first year they will release cut-off for each branch of B.Tech and accordingly you have to choose, so I feel there lies a risk because due to some reason if you couldn't manage to perform well you may not get your preferred branch. BITS Dubai, CSE will great but you need to keep in mind about the fact that you have live there and among all the BITS campus CSE in BITS, Dubai is least preferred due a lot of factors. Thapar institute is great in terms of placement and crowd, they are renowned to offer the best package and they have very limited seats, so it's quite a advantage. Keeping all of this in mind you may select accordingly. All the best.

I hope this was helpful.  Thank you!