Hello David,
Sorry for the late reply.
The screen brightness issue you've encountered might be a side effect of using the monitor driver. Could you please clarify if you have the monitor driver installed on the Host machine? If you're not sure, you can check this in the Host settings:
1. Right-click on the Host icon in the system tray and select
Settings for Host2. Navigate to the
Driver tab. If you have the monitor driver installed, then the
Uninstall button would be clickable:

Please note, that the monitor driver is only needed for the
blank remote screen feature. Therefore, If you do not use the blank remote screen feature, you do not need to install the driver.
You can uninstall it by clicking the Uninstall button. You also avoid the driver installing in the future, if you deselect the
Install monitor driver checkbox when installing the Host:

Here's a related KB article about the monitor driver:
https://www.remoteutilities.com/support/kb/what-is-a-monitor-driver/Hope that helps.