Just added my NUC5i3 to the sheet, and with my library and the measurements taken last night, is giving as good equivalent results as the NUC8i3 (240Gb Kingston m.2 PCI) and NUC7i3 (with Samsung 970 Evo NVMe 250Gb m.2) listed, and just as good as the NUC7i5 (with Samsung 960 M2 SSD).
So it looks like, based on these measurements and statistics that ROCK doesn’t need the additional CPU performance of later NUC generations or faster i5 or i7 processors, or NVMe based SSDs - it is holding its own on a 15W 5th Gen NUC i3 CPU from 2015.
Plus I have still have a NUC5i3 for sale here (a spare, all built with the same components as measured here), advert updated to include these results see FS: NUC5i3 ROCK server