If you appear for only paper 1 then your paper 1 ring will come only and you will be absent in paper 2 but not appearing in paper 2 will not affect your rank in paper 1 and paper 2 does not have any relation with paper 1 therefore it is your choice to appear for paper two because paper one is for bachelor of engineering/ technology and paper 2 is for B Arc.even you can appear for JEE advanced if you qualify paper 1 without appearing in paper 2.