Hello iJimJones,
Welcome to Apple Support Communities!
We want to help review the details of the USB-C Digital AV Multiport Adapter.
See here:
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The USB-C Digital AV Multiport Adapter lets you connect your USB-C-enabled Mac or iPad to an HDMI display, while also connecting a standard USB device and a USB-C charging cable.
This adapter allows you to mirror your Mac or iPad display to your HDMI-enabled TV or display.
3840x2160 at 60Hz on:
iPad Pro 11-inch, iPad Pro 12.9-inch (3rd generation and later), MacBook Pro (16-inch, 2019), MacBook Pro (15-inch, 2017 and later), MacBook Pro (13-inch, four Thunderbolt 3 ports, 2020), MacBook Air (2020), iMac (Retina 5K, 27-inch, 2017 and later), iMac (Retina 4K, 21.5-inch, 2017 and later), and iMac Pro (2017 and later)
1080p at 60Hz or UHD (3840 by 2160) at 30Hz on:
iPad Air (4th generation), MacBook Air (2018 and later), MacBook Pro (13-inch, 2016 and later), MacBook Pro (15-inch, 2016), iMac (non-Retina, 21.5‑inch, 2017), and Mac mini (2018)
Simply connect the adapter to a USB-C or Thunderbolt 3 (USB-C) port on your Mac or iPad and then to your TV or projector via an HDMI cable (sold separately).
Use the standard USB port to connect devices such as your flash drive or camera or a USB cable for syncing and charging your iOS devices. You can also connect a charging cable to the USB-C port to charge your Mac or iPad."
This Apple Support page has the full details: USB-C Digital AV Multiport Adapter - Apple
There isn't a setting based on the adapter being used.You'll want to make any necessary adjustments on your TV or output device.
We hope this helps to understand your best options to use the adapter and change the resolution as needed.
Cheers!
