... and with the info slowly leaked by oicur12.again, imagine what the said airline would have done to the procedures and flows if they ever laid hands on a 'bus.
The CL had a side-slip indicator, and centring that with rudder for level wings and zero ailerons was the training I got, nuances perhaps forgotten. The ball is a mandatory IFR instrument on all aeroplanes, Airbus got away from it by using electronic representation. If the NG has the same - why the hell not use it for OEI?
This so-far unnamed operator sounds like a bunch of bright minds who might insist on blanking the VNAV button, dis-allowing the use of auto-throttle, requiring round dials on NG to mimic TOS., and brutalize the anabolic MAX into operation with no differences training.
It's interesting to observe, whether or not it really transpires there are no technical answers for the OP's questions.
V1 audio: Our training was to announce early enough so as to finish the call by the time V1 is being passed. Worked well, around -3 kts. The present operator demands -5 kt which I find imprecise on the early side, but it is for commonality with the A330 automatic call. Still think it's off by 2 knots.