Hi there, Jee mains is conducted by NTA whereas  NATA is conducted by council of architecture. The Institutes that give admission on basis of jee mains paper 2 are NITs and GFTIs whereas by NATA you get admission into private colleges and state levep colleges. But yes it is not necessary for NITs colleges that you have given NATA exams but for other colleges it is mandatory that you have appear in NATA.

Good luck.