More info about the firmware update on GetOlympus
Here are two video reviews from Robin Wong and Peter Forsgård:
Robin Wong also wrote a blo post and the conclusion says:
I applaud Olympus for providing such a significant update for E-M1 Mark II. After all, this camera has been around since 2016, with the updated and reworked camera features, the new Firmware 3.0 brings E-M1 Mark II closer to E-M1X especially when it comes to AF improvement, which to me is a critical upgrade. This will directly affect the camera performance across all shooting scenarios.
There is also a German written review by Photo Bern.