From which stream you want to do MBA all depends on your interest, in which stream you find yourself comfortable and want to build up your career. Stream selection or which stream will turn out to be bad or good does not at all depends on whether you are an engineer or non engineer or in which stream you have completed your graduation.

Being a B.A. graduate you have some perks like you will be getting additional marks in your aggregate score which is used by top colleges to make a merit list and call students for interview and WSAT round. Also you already have a little idea about some of the subjects which are gonna be taught to you in next 2 years in b-school. Generally even non engineers get a call from b-schools at a little lower percentile than the student of same category.

Regarding stream selection in almost all of the top institutes you get a whole first year to find out a beat stream for you where you are taught subjects from all the streams. And then in second year you are allowed to select all the subjects from any stream you want to study (happens in all IIMs) or select the steam in which you want to do major and minor specialization.

So don't worry about it and concentrate on your preparations and exams. All the best!!