vMix provides a number of tools to assist in vertical video production while still maintaining a standard 16:9 / Widescreen production:

Vertical HD Preset

When selecting New in vMix a number of Vertical HD presets are available for the most common frame rates.
These ensure the vertical portion of the screen is exactly 1080x1920 (3412x1920 in total)

This allows streaming out the vertical portion of the screen in full HD without sacrificing resolution.

NOTE: As Vertical HD (1920p) is larger than HD (1080p), this preset requires either the 4K, Pro or Max editions of vMix.

Safe Areas

A Vertical 9:16 Safe Area option is available to display margins on screen for vertical production.

See Safe Areas for more information.

Source Rotation

Easily rotate Inputs 90 degrees for use in Vertical HD production from the Input Settings - Position tab.
For example video cameras that have been rotated 90 degrees specifically for a vertical production.

GT Vertical Title Templates

A number of animated title templates are included specifically designed to fit within the vertical portion of the screen.