Neet won't be tough but yes the competition will get tougher since AIIMS and JIPMER have been removed and merged into NEET. So cutoffs might rise even higher. And yes only NEET is the common entrance exam for admission to all the medical courses available ie MBBS BDS BAMS BHMS BPT etc. The eligibility cutoff to apply for medical courses in neet last year was 134 marks for the general category and 107 for reserved category. And talking about admission criteria, if you score above this eligibility marks, then you are allowed to be a part of neet counselling. After which, colleges will be allotted to you on merit.

To have a detailed information, you can refer to the following site..

https://medicine.careers360.com/articles/neet-faqs

Best wishes. Thank-you..