Seems DJI changed this a quite a bit from Phantom/Inspire.
Who knows what Downlink Bandwidth 10/20 MHz really means/does?
and what is meant by the cryptic "Cannot use 4K or High Frame Rate to shoot a video in HD mode"?

Hi, Fredz,

You may find the Test Report useful in understanding various modes the MAVIC Pro remote controller is capable to operate.

The downlink bandwidth 10MHz / 20 MHz options refer to the spread spectrum modulation techniques for radio communication. To my understanding, wider bandwidth when comparing with low bandwidth under the same maximum allowable power spectral density can transmit higher data rate, but will be more prone to interference. May be Folks here who are experts in radio communications can correct me if my understanding is incorrect.

I have no idea of your referred cryptic description with respect to the image transmission mode settings.

Henry

The bandwidth relates to the amount of data that can be sent per second.  The 20 MHz bandwidth will yield 1080P preview on your mobile device while flying.  10MHz will yield a 720P preview on your mobile device while flying.   However the The 20 MHz bandwidth setting has far less range and is more prone to interference.

The 10MHz setting will have a more stable long range signal.

The 20 Mhz setting will have higher preview quality but a less stable signal long range.

For the upper part of the setting screen, my understanding is that in general the Auto Channel Mode is preferred, as the Mavic and Controller will channel hop as needed in-flight to always occupy the frequency with the least interference.