Microsoft has made some Windows-based optimizations to things like memory management. But, as far as I know, they've been upstreaming those optimizations back to the Chromium codebase. There are some things that aren't upstreamed like Startup Boost and Game Mode (or whatever they're called) where Edge runs as a minimal background process on login to reduce startup lag when first opening Edge or reduces resource usage when Windows detects that you're playing a game, respectively.
I cannot imagine Microsoft improved Chrome's speed by a noticeable degree without Google noticing and applying the same improvements.