Hey Ondrej,
I believe this is an issue in the highlight alignment if you previewed from the largest size to the tablet size (see video in the secure note). The alignment gets fixed if you open the Laptop preview first then go back to the tablet preview.
Regarding Slider Revolution, I’ll post that as a feature request to be forwarded to ThemePunch.
Regarding the changes in the theme, what I’d recommend is, don’t update your live site yet. Copy your live site to a staging server to learn the changes. This is a big update and the changes were necessary as the new Layout Builder joins the family of builders.
Regarding Retina, our theme is only provides an interface if you want a retina setup. You can disable the retina feature if you want. For more information, please see https://www.smashingmagazine.com/2012/08/towards-retina-web/
Hope that helps.