Vmix uses multiple overlays and frames to produce a variety of frames to be used on your stream.
To manage the switching of these why not use Elgato Stream Deck.
Stream Deck XL puts even more creative power at your fingertips. Meaning you get more studio-level control to optimize your content. More access to time-saving integrations. More scope to boost your production value. More of everything that keeps your stream fresh, and your audience hooked.