It's based on Chromium which uses Blink as its rendering engine, which was forked off WebKit (which was derived from KDE's KHTML and now powers Apple's Safari).

Opera is also based on Blink.

It's more about which features they add/remove etc. So the core will be webkit, and will share those quirks.

Meanwhile we still have stuff like extensions, privacy policies, dev tools, etc. Also they have the ability now to tweak webkit to their needs.

You're right, most "new browsers" are essentially just chromium, I'm hoping since MS is large enough that they'll make it unique in some way - great dev tools and privacy would win me over for example.