Hello everyone! Okay, so here is my setup: I use VoiceMeeter Banana virtual mixer as I am also a streamer, I use a XLR mic with a separate headset and I have not been able to get any comms working in-game. However, after much deliberation mentally and messing around with the terrible Win10 audio settings, I’m happy to announce I’ve found the problem most, if not all, of you are experiencing.
Go into your win10 audio settings by right-clicking on the speaker icon, then “open sound settings”. Now, if you’ve been using this mixer, you should already have it setup to work properly with discord, etc. output and input is set to the correct Voicemeeter in/out and all that. However, if you scroll down all the way, click on “Advanced sound options”, and you’ll see a list of every application that is putting out sound. You’ll also notice they all have “default” output/input. Now, this is where the problem lies. Instead of Reach just using whatever your win10 mic/speaker input/output is, it’s using it’s own, creating multiple audio drivers to run at the same time, and this is why your audio sounds “distorted” or “laggy”, So you’ll need to boot up Reach, THE GAME MUST BE RUNNING OR YOU WON’T SEE IT LISTED IN APP VOLUME AND DEVICE PREFERENCES here, once you see it listed, change the out/in to the exact same thing you have it as in the default win10 input/output. meaning, when you first open the sound settings before you click on “advanced sound options” those input/output settings should match what the settings are specifically for Reach in the “advanced sound options” panel.
You can prove this to yourself by loading up a custom multiplayer game and then go into these settings, when you change the game-app out/in for Reach specifically, you’ll notice that all that distortion/lagginess goes away. So it’s clearly a driver issue.
This would be easier to explain with pics, but idk how to do that here, so if anyone needs pics or a better explanation, feel free to ask here or tell me how to post pics in this thread and I’d be happy to 
Hope this helps you guys, and happy hunting Spartans!
*Edit: For those who are not using any complicated communications setup, simply run the game and go into the “advanced sound options”, and make sure that the input/output is set to your headset or whatever mic/speaker setup you are using. This will force the game to use ONLY that input/output and should solve your issues.