Exactly what the title says, for example, i know people who do short films, anywhere from 1 to 30 minutes of duration and they even make some longer films, they are awesome, but the point its, are the videos stricly youtube shorts/tiktok like or can they have any other aspect ratio and how long can they be?

I believe the idea is a youtube short format (<3 Minutes) and vertically oriented.

The videos are pitches for the game. IT would be a short video explaining what's in your game. So, a youtube shirt format makes sense