The title of the video is "best graphics" so it's really about whatever semantic definition DF gives that phrase. And they didn't explicitly state what that phrase means to them in this video, but given their catalog of work my personal understanding of their view is that they appreciate and analyze how various techniques are applied towards an end result, considering the hardware it's running on. It's not one or the other between technical make-up and end-result of the aesthetics for them. It's about the ingenuity and implementation of said techniques towards a final goal that each individual project is trying to achieve. That's why they can have proper discussion and analysis of games on older or less powerful hardware and still appreciate the outcomes. 

As for why they didn't name games like Witcher 3 and Doom... Well again I'll point to the title. It literally says "First Party Exclusive Selection". Doom and Witcher 3 aren't first-party or exclusives. And they reiterate that at 1:08 in the video. They make exceptions to their own rules with Fast RMX and The Touryst, but that's because they aren't robots. John has touted his admiration of that (non-first party) studio for the decade he's been there and is always open to highlighting their works. The studio also has a long-standing closeness to Nintendo hardware with Fast RMX being an expanded port of a Wii U exclusive, The Touryst debuting on Switch before coming to other platforms, and most of the studio's output being exclusive to Nintendo platforms.

In a simplified way of speaking, yes. The higher quality settings are usually just higher "sample rates" (you can think of this as resolution) versions of the same effect. They can also be completely different techniques/ways of doing the same kind of effect but requiring much more processing power. That's what "optimization" is. It's about setting the right "resolution" for the different effects and/or finding the right technique to do the same thing but with less processing power, usually at a reduced quality of end result but weighing the performance cost to quality. For example, there are many ways to blur a frame/image, or apply "depth of field" to it. Typically the "better" techniques (those that better resemble how a camera or eyeball works) require more processing power. But you can get away with a cheaper technique if it's used the right way or during the right moments in a game (like maybe only using depth-of-field during cutscenes when action is more controlled, the framerate is lower, or the CPU is freed from processing game logic).

Nah, the textures on ToTK are atrocious at times. BoTW is nicer looking.

They look pretty much the same to me texture wise; DF didn't highlight any shortcoming there in their analysis either. Not sure why textures would go backwards when moving from a game built for Wii U to a game built for the more capable Switch.

Also think crysis 3 is the best looking on FPS on switch another 7th gen game which switch really fixes. very surprised MGSV never made it seems like easy money.

Yeah Crysis 3 is one of the best looking third party Switch games in my book too, though I'd actually say Crysis 2 Remastered looks even better as it got a more extensive upgrade including an all new lighting system, whereas 3 mostly just improved the resolution, AA, framerate and textures.

Wonder why did not add  SVOGI in crysis 3 for switch, was the lighting already good enough or too taxing?

I honestly don't know; the original lighting does already look really good in my opinion so it could a matter of "it costs us 3fps of frame time but doesn't look that much better".

Again this is about DF best looking games not games using the most advanced feature set, if it was about the games with most advanced graphics features they would have actually named games like witcher 3 and doom arent on the list and do you know why it's because they look like mud. botw runs on hardware objectly  weaker then the 360 yet you named it as the most impressive open world game just a few posts ago, when we know witcher 3 is way more advanced so you are allowed to do it but i'm not?

They look pretty much the same to me texture wise; DF didn't highlight any shortcoming there in their analysis either. Not sure why textures would go backwards when moving from a game built for Wii U to a game built for the more capable Switch.

No SVOGI, due to art driven GI that was the reason, just found it on resetera.