I'm collecting my used 2016 RRS next week and have been reading-up.

It seems there's no way of configuring the instrument cluster (speedo, rev etc). I assumed it was an LCD screen because there were different user-configurable set-ups. But it seems this isn't the case.

If no, what is suddenly so wrong with mechanical dials?

Welcome to the Forum.
I thought the 'head up' and 'electronic' displays were an option, (other than electronic speed readout) not fitted on most as standard, what model is yours? On the readout you can switch to KPH I believe. John

RRS MY12 SDV6 HSE. Sumatra Black/Ebony & Walnut + Dynamic Pack, + Cold Climate Pack + Memory Pack, Digital TV/DVD, Premium Leather, Cornering Lights, Cooler/Fridge Box, & most Options.