Good questions; it's fairly common and appropriate to focus on say 2-5 key things you'd like to get across about yourself (2-3 main points probably most appropriate). I'd focus on the main things you are trying to emphasize in your overall application... another way to think about it, how would you like to be remembered by the admissions committee?? Are you 'the investment banker who climbed Everest for charity', are you 'the engineer who spent time tutoring kindergarteners', are you 'the passionate entrepreneur who loves travel and cooking', 'the accountant from Brazil who is known for leading teams...' you get the idea! Think about key experiences, traits, and facts about you that are memorable and 'summarize' who you are if possible, and use those as a starting point.
As for format, either way works... they wouldn't have given you a choice if they had a preferred option. I would say do whichever you feel like YOU can present yourself the best with! The video option can be high risk/high reward... it can be more risky for sure, and has the potential to fall flat or not come out as you'd like... but if done effectively, can sometimes be more memorable or make more of an impact on a viewer, that's just human nature. That said, a solid and compelling essay can be very effective as well.
Good luck!