Just to add my perspective....
There's no difference in the PMIR and BM selection process, except for the fact that there is a GD and interview for PMIR, and only an interview for BM.
As far as acads go, yes, acads carry some weightage in the final tally of your score, after you crack XAT. If you clear all cutoffs in XAT, then, your acads, workex, and overall profile are given some weightage in your final score, along with your interview performance.
People who think their acads are bad - go through my record - Class X - 85%, Class XII - 67%, B.E. - 62%
Also, there's absolutely no need to worry if you don't have workex, and no need to gloat over things if you do. Ultimately, an interview is all about what you are, as a person. So focus on highlighting your personality during the interview.
But then, all that needs to be thought about only after you qualify the exam. So, I'd say stop bothering about acads, interviews, workex etc. because on the day of the XAT exam, everyone is equal. Only after you prove yourself there, you need to worry about those things.
And then, of course, you'll have a lot of support from us throughout, so prioritize!!
All the best!!