I've been working a bit on modifying some existing skins for use with a small raspberry screen. Changes are driven by lack of space on the screen because I will likely will end up with one of the 480x800 screens that are readily available. Since most of the existing skins are based around 1080 or 720. is it worth my effort to redefine the resolution for the skin to be 480x800? It's not clear to me if there is a performance advantage or image quality benefit. To say it another way, should I let kodi rescale everything for the lower resolution screen, or should I go to the effort to resize all the buttons/controls/icons/etc.
Kodi will do the math and downscale all the dimensions. The only thing you might want to do is resize the textures yourself.
To be clear, it's sufficient to simply adjust <width> and <height>. Let Kodi take care of resizing the whatever is stored in textures.xbt.
I recently did a project where I used Kodi with a Pi touchscreen (which is the same resolution I mentioned and might be the screen you're using). The thing I really noticed with Estuary is that the click/touch targets get *really* small, so you might want to look at Estouchy (the touch version of Estuary). I ended up sticking with the stock Estuary (for reasons), but that came with some usability trade offs for sure.
The real estate issue is one of the primary reasons for the modifications. Every pixel counts with only 384,000 on a 5 inch screen.