" Previously, Epic Games’ Fortnite has bucked this trend by allowing players to natively voice chat within the game simply by connecting a headset with an integrated microphone.
Overwatch follows in its footsteps, making use of Blizzard servers to host voice chat for any and everyone playing on Switch. This cuts out the middle man and makes engaging in voice chat a far simple and more refined process, which should hopefully also entice a greater number of players to bust out their microphones and start playing the first-person shooter to the best of their (and also their teammates’) ability."
htt ps://www.gamerevolution.com/guides/607861-overwatch-switch-voice-chat
Basically I tried VC on splatoon 2 a couple years ago. You needed an audio splitter to the nintendo switch that allowed two inputs one from an iphone or other and one from a mic. The iphone ran an app that would essentially run the the voice chat via third party app.
However, all we need for Overwatch is apparently a 3.5 mm plug in so everything works with no phone needed.