I've been using Scale to Fit Width in export and it adds some code along these lines:
<style id="xr_scstrchs">.xr_scstrch{width:100%;left:0%;z-index:-1;}</style>
<script>xr_fitwidth=1280;xr_fws=1.50</script>

It works but when the page loads on mobile it takes a beat to readjust to the viewport size.
That's fine, I just wonder if someone knows more in depth what is happening.
Maybe it can be tweaked for a smoother scaling transition?
Thanks