I was thinking from the 19x's point of view in a mechanical sense (where the couplers, electronics, and pull-away tests are based on the same hardware), and maybe not enough about how the driver's procedure is different. Regardless, thank you for the reminder about the operation as a whole.The 197s are completely different to couple than the 195s, there's a cab wall panel with cab equipment to unlock move then lock into position.
Then unlock the first inner door move then lock into position, next step is to unlock and lock the floor leveling plate, finally unlock the concatener doors then move and relock safely.
Then you start the coupling procedures draw 6ft then 2ft, check couple alignment and press coupling speed control to power onto unit and then the unit runs coupling and test procedures.... then the driver ensures brake release try doing that in 3mins.......
Also the 197s electrical boxes are located in a different configuration than the 195s.
Early in the TfW franchise I had a layman's go at drawing up an indicative timetable for the North Wales Coast based on the announced services. I remember that routeing the services to/from Liverpool was the most challenging: they needed to pass each other at Chester while coupling/uncoupling there (occupying two through platforms in the process), and being constrained by the single track portions to Wrexham and short turnaround times for the Shrewsbury terminators.
From memory I had the two separate units arriving into Chester seven and five minutes before departure for Liverpool (and vice versa in the other direction). That might be practical with a 3-minute coupling on a 158, but a 9-minute coupling would clearly blow that out of the water. It'd mean through passengers might be timetabled to sit at Chester for 12-15 minutes: in that sort of scenario you might as well ditch the coupling and ask one set of passengers to change train!