Hello Aspirant

If you give JEE Mains paper-2 you can get a seat for Architecture at an NIT. But, to get a B. Arch. seat in an IIT, paper-2 plays no role at all.

So, if your goal is just to get into the NITs then you will just have to appear for Paper-2, and if you want to get into a IIT, you will have to give:

JEE Mains Paper-1

Qualify JEE Advanced

Qualify AAT (Architecture Aptitude Test)

Hope this helps