These are the setting used in the linked video.
To change preferences, Select from the Main Menu Edit->Preferences.
In the general category, Imperial units specifically formatted for building.
In Draft Arrow Size, Font Size and Text Spacing where changed.
In the Arch workbench, only Wall and Windows were changed to more closely resemble US constructions. Keep in mind that currently only metric entry is permitted in the preferences tab. You will have to convert Imperial to Metric.
Wall were set to 3.5 Inches Thick and 8 ft tall.
Windows were set to 3 feet x 3 feet.
The draft Grid settings use 12″ spacing. The easiest way to set the Draft Grid spacing is by clicking on the working plane tool. ( make sure you have nothing selecting in view )
Grid spacing can then be set in the “Select Plane” dialog.