We learned earlier here at Microsoft's Build 2019 developer conference in Seattle that Microsoft's Chrome browser on Chromium will have an IE Mode in which is opens up sites and applications that would have required legacy Internet Explorer applications in the past. But it won't just happen. There's a little bit of work to be done. I tried out the new features announced at Build, including IE Mode, the macOS version and Edge's new privacy features.
You can try Edge on Chromium now by joining the Edge Insider, but these features have yet to hit those builds.
Getting Sites to Work in IE Mode
Specifically, people who work on Edge told me, site administrators will need to make some changes to their sitelist. Instead of opening in IE, those people will need to tell the apps to use MSHTML (a proprietary engine used for Internet Explorer) to open in Edge instead of the older browser. That is what will make the new Edge show a small Internet Explorer icon when it opens the page - successfully - without punting you to an older browser.
Once that happens, it will work in Edge on any version of Windows that supports it (meaning Windows 7 on up). But it's not on the roadmap for Mac support, I was told, because it needs to support Internet Explorer to work. That OS, unsurprisingly, doesn't.
Once those changes are made to sites, however, they will act in Edge like any other site or web app. They'll even show up in the same history, I'm told, and won't be separated.
Security and Privacy Options
Edge developers showed me the new security settings (it was on the macOS version, see below). It shows the three options, and Balanced, which allows trackers on sites you've already visited, will be the default. Basic is the internet as it stands, which allows the use of data to be collected to target ads, and strict will block all third-party trackers. The latter may break some websites.
macOS Version Coming Soon
I also got a brief hands-on with the new macOS version of Edge. Unsurprisingly, it's basically identical, and I was told they're going for "few or no differences" between the Windows and Mac versions. No release date was given for the Mac version, which will be released in Developer, Beta and Canary versions for testing, just like it currently is on Windows.