I've now tried both methods of topology (getting a bit tired of soldering now tbh ).
Cables are just butchered Jumper wires - so nothing special or shielded.

Anyways - Both seem to work reliably.
ie data gets sent without corruption.

My one issue is teh speed at which it writes teh data to teh displays.
I appreciate from previous comments, that I may be pushing the limits of this type of bus with my setup - but can anyone suggest any things I can do to speed up the writting to the displays pls.
As the displays are located next to each other in a single row of 8, the data writing appears like a ripple/domino effect from LHS display to RHS display.

I'm sending 2 rows of 4 char strings (max) to each display.
Even teh data writing to one display exhibits the same ripple/domino behaviour.