You're probably already well aware on how to enforce settings, using MCX or profiles. If not, I will talk about it anyway soon.

Here, we want to use something similar to the MCX "Once". This means, we'll set the preferences during first run, and then will let the user decide if he/she wants to keep our suggestions.

To do that, we'll create a file "/Library/Google/Google Chrome Master Preferences"

Use these pages as a reference -> https://support.google.com/chrome/a/answer/187948 and https://www.chromium.org/administrators/configuring-other-preferences (may not be up to date)

I used this one to test: 

If you want to delete every user Preferences and Cache, and launch Chrome as if it was its first run, use the following command:

-> Good ressource on Google Chrome's Command Line options