All of the "official" formats beyond DD and DTS are only 6.1. DD EX and DTS ES are 6.1 formats with a "matrixed" back surround channel. This 6th channel is extracted from the L&R side surrounds like the center is from the mains in Pro-Logic.

DTS ES Discrete is also a 6.1, but the rear channel is discrete and does not depend upon the side surrounds.

7.1 usually refers to taking the single back surround channel and splitting it into two amplifiers and two speakers. This is done to enlarge the sweet spot for the listeners.

Any 7 channel "modes" are propriatary DSP processing that makes 7 channels from 2 or 5 discrete channels. They can be nice, but are not built into the software.

5.1 and 7.1 stereo modes is just a way to take a 2 channel source and pipe it though 5 or 7 speakers to fill the room (good for parties). No processing is involved. They just take some or the right channel and pipe it through the right side surorunds and the same for the left side. The center is a L&R blend. Nothing magic here, just room filling sound without distroying the original 2 channel imaging.