JEE

You can get good branch in srm but the choice needs to be yours.

http://www.srmuniv.ac.in/admission-india/management/admission-procedure-admission-criteria
Please check if you match all the criteria for admission in SRM and according to your question this course is available only in the main campus. Have a look on the course available:
http://www.srmuniv.ac.in/admission-india/management/programs-offered

You can check on the college predictor that which colleges you are getting on the basis of your rank:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor

We cannot decide allotment to IHMs. It is based on numerous factors- No. of students appeared, no. of students passed, merit list, vacancies, reservation, demand for admission, etc.
But for reference, you could use past statistics (it is available on NCHMCT Facebook page). But that cannot be a solid reference line for this year's admission.

If you are really confident that you are going to beat JEE Mains the coming year, droping this year is a very good choice.

Yes, you can apply for JJ College of Architecture. I have no knowledge regarding COEP.

Yes, MBM is a good engineering college located in Rajasthan. Placements are also good there. You should go for that.

Yes, the counsellings for JEE Mains and Advanced will be held separately.
First, JEE Mains counselling will be held.

Yes, you can easily get that stream without any problem and you can also get admission in IITs.