I've used "Unbounce" previously and they have a feature that allows you to decide if you want an element that you're adding to a landing page to be visible on both desktop and mobile or just one or the other. As an example, I have loaded a video onto a funnel page and I have reduced the size of the video player.

This has forced the video to be displayed off-center. I have manually adjusted the player to be centered but it is centered on desktop but very far right on mobile. In the case of Unbounce, I would be able to upload one video on desktop, then center it. When I look at my mobile view, I would see that it is misaligned so I could make the video player invisible on mobile.

I could then upload a the same video a 2nd time and center it on mobile, then make that element invisible on the desktop view.

So 2 videos would be present on the page but only 1 of them would display on mobile and the other would display on desktop.

I could ensure that both videos are centered on their respective layouts.