It's likely got nothing to do with MacOS - the operating system is capable of running video chat in an efficient way. Just look at all the other similar apps which run fine - Zoom, Skype, Hangouts, etc.
The issue looks to be with the implementation of the video chat in Teams. It could be an issue with Electron, which is the framework on which Teams is built. Or it could be in an issue with the Teams implementation of it. Either way, I am hopeful it's fixable in a future Teams release.
In the meantime I've had to splurge on an external graphics card for my MacBook Pro, which has eliminated the performance problems Teams was causing every time a video call was launched. <-this actually works. That said, one shouldn't have to buy a high end gaming GPU just to run their work chat software.