The question: replace the two text faces, Archivo for titles and IBM Plex Sans for language, with Inter carrying both, using its optical size axis so titles and body come from one family. Mono stays IBM Plex Mono in both treatments; a number is data and this lab does not touch it.
Readability under big content is the deciding factor, so every specimen below is real platform content at real platform sizes, and the dense register appears in full, twice. A · Archivo + Plex Sans B · Inter, one family
Drawn fresh from the Untitled kit and the system’s ruled tokens, not restyled from the originals.
The blue rules sit at the same height in both columns. Inter's x-height is visibly taller at the same point size, which is the single biggest reason it reads more easily at 12.5px: more of every letter lives in the zone your eye scans.
All Customers from Lab 05, identical data, identical widths, identical mono columns. Only the language face changes; scan for the customer names, which is the reading a person does two hundred times a day.
Side by side comparisons let the eye cheat by comparing shapes instead of reading. The button at the bottom of the screen flips this one section in place, same pixels, which is how a real difference in reading comfort shows itself.
Titles do their real work on the customer side, where the document is the product. This is the one place Archivo's identity earns money, and the one place Inter's neutrality costs most, or reads most professional, depending on the eye. Yours decides.
At body size, B is the easier read: taller x-height, wider apertures on a e s c, and Inter's optical size axis serves a slightly sturdier cut at small sizes automatically. At title size, A has the identity: Archivo's width axis gives the platform its wide, engineered voice, and Inter at display size is deliberately neutral, closer to a very good system font. The trade is real in both directions, which is why the next two sections show whole screens instead of specimens.
Names in B sit larger on the same 31px row without the row growing, because the extra size is x-height, not ascenders. Weight 500 in Inter reads a touch heavier than Plex's 500, so bold names separate from plain cells slightly more. The cost is width: Inter sets a little wider at the same size, so "Aurora Travel Partners" and the agent column consume a few more pixels each, which on a ten column register is the difference that eventually pushes a column into the scroll.