>>1. Should we focus on the app itself and demonstrating the UI/UX, or make it more feel-good/people/marketing oriented?<<
Without knowing your app and your business plan it is hard to specifically answer the question. So understand what the purpose of the video is:
Put yourself in the shoes of the person whom you want to buy your app, but who doesn't understand your app. Your video is essentially your Cold Call pitch. You have about 3 minutes to tell your Cold Call story. And you have about 15 seconds of run in to capture my attention as to why I should care about your app and why I should spend an additional 2:45 watching your video.
Even if you offer a Free Trial for your app, or your app is free and your monetization strategy is via ads or some other method - YOU STILL NEED TO CONVINCE ME TO INSTALL.
And THAT is what your video needs to do. So as a potential user, I need to
That is what your video needs to do