CSS Shapes is now on the Microsoft Edge backlog with a priority of medium. You can track status updates at https://dev.modern.ie/platform/status/shapes/
I just want to bring to attention, that this feature would have been great, even just a year ago, but as of today, this is actually mostly deprecated.
If you are still using floats for anything, you should really get to know flexbox (The only exception if you need to support IE9 (or lower?? i feel sorry for you))
Anything you are building with floats, is a lot easier with flexbox.
Disabling collapsing margins can also be done with display: flex.
Really point your attention to flexbox/grid way of styling with the help of @support for some backwards compatibility rules, because floats and clearfixes are pretty much dead already.
If you want to improve the future of CSS instead of the past: Put your vote in this issue: https://wpdev.uservoice.com/forums/257854-microsoft-edge-developer/suggestions/10938981-implement-the-box-generation-keywords-from-css-dis?page=5&per_page=20
It will enable us to use Grid layouts to it's full power, and even solve some other minor CSS annoyences. It will allow us to "ignore" boxes, so you would be able to do things like ul.menu > a.link instead of ul.menu > li.item > a.link (just a stupid example, ignoring list items, it can have some powerful implementations).
for grid layouts it means you could take children from nested boxes, and put them in your main grid.
Now that display grid is available in all browsers and having used it in a couple of production sites, there is one thing still missing for it to become truly useful. Semantics of webpages greatly reduce the usability of grid. I'm noticing i'm still resorting back to flexbox because, at the moment, for "normal" layouts, grid offers very little advantages in practice. With display:contents we would be able to really use the power of grid layouts. Please consider this before the "implement CSS `display: flow-root` (modern clearfix)" because that feature is mostly deprecated because of flexbox/grid.
CSS Clip Path is currently on the backlog with medium priority. The status can be tracked along with CSS Masking at https://developer.microsoft.com/en-us/microsoft-edge/platform/status/masks/
You guys have 2 more firefox versions to catch up! I believe!