Hello! Leonardo Reyes
1. YT video section can be replaced with only <iframe> contents. If you want to replace YT video with another video that must be inside <iframe> tag.
But if you want to upload the video from your file then you can use Video Gallery Section where you can upload your own video and customize “Slide To Show to 1”. Uploading size depends on your site WordPress file upload limit, Smaller the size faster your site loads. Thank You! Hope this helps you.