The decorative Devroye smallcaps font that I tried before, only comes in that italic version.
Here I have used Andada slab-serif smallcaps in regular (I used this elsewhere for chapter titles, etc), the second segment in the middle of the page is Andada SC italic, and the third segment is Alegreya. Screen-shots show Serif and Sans-serif body font.
Looks like the Andada font weight blends better with the Sigil previewer body fonts, but I don't know yet how it will look on a device.