You can duplicate your website and redesign it, but you can't then move that design back to your original website, you need to purchase a new subscription and cancel the old one plus move your domain and other settings, some very manually. It's not ideal.
There's currently no way to put your website into draft mode, but you can redesign pages and keep them disabled, then swap out pages when you're done, the downside here is that if you want a major change to the styles (colours/fonts etc.) you can't easily change those without affecting your live website.
There are a number of reasons why videos may not autoplay (for example power save mode is on or low data rates are available) however your videos are autoplaying for me in Safari.
