Are first round interviews accounted for in the second/final rounds

I can only speak for McKinsey but the answer is "a little". The only thing that carries over from your 1st to 2nd round are your actual scores on your PEI and Case performance. Those scores are put up there with your scores with your second round. There are no notes put up from your first round (so not notes about "Why Consulting", "Why McKinsey" or your PEI stories). The partners then discuss your 2nd round performance from their performance note. So, it's really all about the 2nd round performance and if there are questions about a read on a particular area, they will refer back to the first round scores. In extreme cases, they will try to pull the comments from the assessment sheets, but 70% of interviewers take awful notes or none at all.