While I can't speak to the completeness of the Google Chrome account sync, All of the settings for your Google Chrome account are kept in your user profile.
So there are a couple of ways to proceed
- Keep a current backup of at least your user profile using the backup utility of your choice.
- Time Machine works well for #1 above as it backs up your user profile by default (in addition to everything else.)
- You can use the Migration Assistant to migrate your entire user profile (Apps, too) from your old Mac to any new Mac as long as you have a backup or access to the HD or SSD in your old Mac. This includes the still working old Mac attached to the new one with an ethernet cable.
I don't use Chrome much but if I recall correctly there are preferences and folders that contain all of Chrome's configuration files, cache, bookmarks, add-ons and whatnot located in your
~/Library/ folder. That is the Library folder inside your user profile that is usually hidden from view in Finder.