Looking for details on Dynamic Range vs ISO

Question

I have been reading up on maximizing dynamic range of digital sensors in order to get a rich image and soft roll-offs. One thing that I cannot wrap my head around are the following concepts and the combination of them:

1. Digital sensors tend to push multiple steps of dynamic range below 18% grey when the ISO is decreased. To maximize dynamic range in both shadows and highlights and get softer roll-off it seems right to shoot at higher ISO.

2. Simultaneously, there seems to be a pretty wide consensus that exposing to the right (ETTR) yields best results in terms of dynamic range for digital sensors. This indirectly implies lowering the ISO to keep highlight from clipping. Or must ETTR be combined with ND filters som these purposes?
3. Multiple sources suggest that shooting above native sensor ISO could yield further movement of dynamic range steps above 18% grey - could this really be true?
4. The chart shown in the image suggests that dynamic range in highlights/shadows is relative to 18% grey. Is that most often true?
5. This site and many others imply that overall dynamic range is lost at higher ISO: https://photonstophotos.net/Charts/PDR.htm.

The only conclusion I can positively draw is that light scenes should be shot at slightly higher ISO to maximize highlights dynamic range while dark scenes should be shot at low ISO to maximize shadow dynamic range. But I can't figure out how to apply ETTR technique to this line of reasoning.

I am aware of the confusing nature of the question, but I cannot boil it down more due to my lack of further understanding in the topic. Any input is much appreciated.

Answer 1

Your points #1, #3, and #4 are regarding the processing Canon applies to video files being saved in the C-log (Canon Log) format. There is processing applied to the data coming off the sensor before it is saved. So technically speaking it is not a "pure" raw format. As this applies only to video recording, it is expressly off topic here. For video only related questions, please visit Video Production SE.

Regarding points #2 and #5, they've been pretty well covered in these two questions here at Photography SE.

Is it better to shoot with a higher ISO, or use lower ISO and raise the exposure in post-processing?
Should higher ISOs really be preferred (all other things being equal)?

There are also several other questions and answers which you might find helpful:

What is "ISO" on a digital camera? (Please be sure to read all of the answers and comments, as they allow the larger picture to be seen. The accepted answer is a bit limited and incorrectly describes ISO as sensor sensitivity when, in fact, with digital sensors ISO affects analog amplification of the signal collected by the sensor. Any particular digital sensor has only one sensitivity.)

Why would using higher ISO and faster shutter speed yield more noise than using lower ISO and slower shutter speed?

Is it really better to shoot at full-stop ISOs?

From a comment by the OP:

I believe still images also can be taken in log formats.

Even if they could, those would not be true "raw" files. There's a LOT of processing that goes on between the sensor and the memory card with C-Log, S-Log, or whatever other manufacturers call it. As such, the answer to each format might be different, depending on exactly how that format (C-Log1, C-Log2, S-Log, etc.) processes the data from the sensor before it is stored.

Video creators might call this "raw video", but it's really more analogous to what happens with still images when we use one app, such as the manufacturer's raw processing software, to convert raw files to 16-bit TIFF files before processing those TIFF files with another software, such as Photoshop. A LOT gets "baked in" between .cr2, .NEF, etc. and TIFF. It's just that with a 16-bit TIFF there's still much more latitude to adjust color, brightness curves, etc. before converting to an 8-bit output without running into the problems associated with trying to do that with lower bit-depth files. In the same way, a LOT gets baked in between the sensor output and a C-Log (or S-Log, etc.) file. But there's still more information there that can be exploited than if one outputs to a lower bit-depth format.