Hello aspirant, hope you are doing good.

Firstly, congratulations for your excellent rank in JEE Mains, scoring so much in such a difficult exam is not at all easy and I'm sure you gave your best. Now, with your rank , you will definitely get a seat in SPA delhi, and infact many other great colleges like NITs.

You can use our college predictor link to find out all the possible colleges you can get into with your JEE Mains rank:

https://engineering.careers360.com/jee-main-architecture-college-predictor?ici=cp-listing_engineering&icn=JEE-Main-Architecture-College-Predictor

As for B.planning , there is a vast scope in this field , in India. You can be a Regional planner , Urban planner , Interior Designer, Design Architect , Project planner and many more such important and respectable positions. The placement scenarios depend on various factors, and considering your rank,  you can get obviously get the best colleges in India, so obviously the placements are also going to be great in them.

You can read more about it here:

https://www.careers360.com/courses/b-plan-bachelor-of-planning

Hope this helps you. Good Luck!!