Journalist reviews of the driving experience aren't available yet. And no one outside of Ford's control has been able to drive it.
That said, it appears there will be six levels of regenerative braking on the Mustang Mach-E. Each drive mode (whisper, engaged, unbridled) has a different acceleration and braking feel. And regardless of mode, you can turn on or off one pedal driving.
Re-reading your post, I realize you're asking for maximum kW for regenerative energy. We don't know that either... But it can't be more than peak power at the motors, which is between 198 to ~342 kW depending on the drivetrain setup.
Haha but Porsche doesn't support one pedal driving. They think it's more efficient to just coast. I find that odd because you can simply adjust your foot to coast if you need to. They blend their regen with their brakes.