Q1: do modular cables differ meaningfully in quality?

They can. But for the most part, they don't. You can get hi-tweak patchcables with all sorts of voodoo to 'em, but those are somewhat pointless; using silver Mogami cables or some such makes far more sense on LONG cable runs, and not little 1m or less lengths.
-- Lugia

Hi Lugia,

Don't we all have at least a ballroom size studio of at least 60 feet/20 metres long wall with our Euroracks against it, hence we need (very) long cables? ;-)

Kind regards, Garfield.

For review reports of Eurorack modules, please refer to https://garfieldmodular.net/ for PDF formatted downloads