In the case of the featured sections in the first screenshot, there should at minimum be a visual well indicating the horizontally scrollable strips. Invisible scroll panes are insane.
They’ve already made it obvious that the row is horizontally scrollable by leaving part of the next icon visible at the right edge. That's a clear (and standard) visual cue that there’s more content off-screen.
But... does the whole page scroll at once, and can I tap and drag "between" two rows (slightly above one, slightly below the other) to scroll the whole page? Or does each row scroll independently, and only taps on the row scroll? I habitually don't tap on anything that looks like an icon if I want to scroll around, because I'm afraid I'll activate the icon in a poorly written program (or if I tap too lightly and it is picked up as a tap and not a hold and drag event). So visual cues as to what's scrollable makes it easier for folks like me to know where to tap to scroll things properly.
this is an interesting take. I've never noticed but I just scroll by using a scrolling motion wherever on the screen, and I don't ever seem to hit a button by accident. It sounds like you are purposefully trying to find empty parts of the screen in order to scroll without the risk of hitting buttons. Modern devices are pretty good at figuring out whether you're scrolling or tapping tho. Have you tried just using a scrolling motion and not worrying about the location?
What happens if my screen width is a multiple of their icon size?
the icons can be scaled with the screen to always have a half icon on the end, just as other layouts scale the icons to always fit a whole number within the screen.
If that clipped column of icons were like K-9's, which has a transparent background and left padding, those clipped icons wouldn't be visible.
Redundancy would be fine. It would help in edge-cases like that.