Video editing is one of the most computing-intensive activities around, so you'll want the best laptop or desktop you can afford if you're serious about cutting your own movies. Most applications help speed up the editing process by creating a proxy file of lower resolution, so that normal editing and previewing aren't slowed down by the huge full-resolution files.
If you’ve got a fitness app, you might have segmented your potential audience into 2 groups. Men who want to get huge lifting weights, and men who want to get ready for a marathon. As you can imagine, they have completely different goals, and their interests and behaviour will reflect that. You need to take this into consideration when you create your images.