How safe is IE?
I suspect the core browser is relatively safe under most condition. So, not significantly worse than Chrome or Firefox, though not as good as Firefox + anal NoScript.
However, historically, MS has always pushed tight integration between products/OS/data (weren't we treated to a little HTA-runs-wo-protection-on-Word recently? Very 90s stuff)
Because of that I don't know if there is enough of a moat between IE or Edge and the underlying Windows OS. I suspect it is way better than in the old days, but I do know that Firefox or Chrome are not treated preferentially by Windows.
If the browser's protection (and NoScript) fail, there is an extra layer where Windows might possibly/maybe/blue moon catch the attack and I expect that extra layer to be even more porous with IE/Edge because of MS's desire for integration.
That, and I plain don't like Edge, for example that you have to jump hoops to display a bookmark toolbar by default - I don't want to rely on a search wizard all the time.
Firefox 1st, Chrome 2nd, Vivaldi 3rd. Edge a very distant 4th.
I.e. (no pun intended) the Windows Explorer blending into Edge/IE referred to in the article is not a feature in my view, it's symptomatic of extra risks.