No, if you look at the image sizes again, you'll see they're exactly the same.
Exactly the same pixel dimensions, that is. And that's the only thing that matters.
So the answer is: either method is fine. They both give the right result.
By "stripping out the profile" they mean to uncheck the profile box in the Save As dialog when you're saving the file.
I don't know what to tell you, sorry. This is just down to luck, it seems.
The first one is completely irrelevant, because you must work in changing light.
The second one ... well, that functionality is in Photoshop already, so I'm not sure what the benefit would be.
The third on ... how many screens do you have?
You can only judge sharpness at 100%. View both files with the Loupe in Bridge.
You can see me using the Loupe in this video.
Never use, or trust, Windows viewer for anything. Only ever use Bridge.
I get the same error message
I don't know if there's anything you can do, sorry. I've spent some time googling "dng file repair", as I'm sure you've done yourself, but there don't seem to be any good solutions leaping out at me.