I have the same question this person asked on that post back in 2018: https://www.wix.com/corvid/forum/community-discussion/responsive-site-auto-adjusting-strip-image-to-screen-size
We’re now in 2020 but it seems that Wix is still having that limitation. I’m trying to get a fullscreen design but I never found a way to do this.
Also trying to make some srtips resized automatically depending on the screen width but the design is just being cut off
Hey,
Start from checking out currently open Responsive Sites feature request here . You can see that a number of elements (including strips) are full-width and responsive.
You can also see that we are currently working to make Editor X perfect for you.
Introducing Editor X!
Note: it’s not yet available for all users.
If you want to know more, you would be better suited going through Wix Customer Care about this issue as they know best.
https://support.wix.com/en/article/contacting-wix-customer-care-for-support
Thank you so much for your reply 
Well I was actually referring to full screen strips because even the current ones are supporting full width but it still does not support full screen which results in cutting off what;s on the strip [like an image background] if you minimize the browser.
and YES! I have already received an email from wix about Editor X and I sent a request as they gave that option to me but I never heard back from them since then!