We cover a larger time period than the 18 day Mahabharata war, starting from the ancestry of the Pandavas and the Kauravas, the circumstances which led to the war, and till the end of the war. But, yes, many of the rounds are themed around the great Yodhdha's (warriors) from the Mahabharata.

I believe the same goes for WSC as well that the 18 videos are a teaser for the round themes and/or names.

Yes that is correct, each video is the inspiration for one round.