Be prepared to provide us the Advertiser ID and Agency ID for the ChannelMix Profile you are requesting to be setup. The easiest way to find these in the user interface is to navigate to Search Ads 360 Campaign Management and select the specific advertiser for which you'd like to pull data. Once you are there you should be able to get these values out of the URL:
ay=20100000000XXXXXX (Agency ID)
av=21700000001XXXXXX (Advertiser ID)
Once we receive your request we can construct the datasets for you. No need to build a report in the user interface.
The standard dataset for Google Search Ads 360 are documented below. They are a great place to start if you are new to reporting with this source.