Just noticed that for me (on ubuntu at least) the default provider sends a lot of stuff as well as the query!

{google:baseURL}search?q=%s&client=ubuntu&channel=cs&{google:RLZ}{google:originalQueryForSuggestion}{google:assistedQueryStats}{google:searchFieldtrialParameter}{google:searchClient}{google:sourceId}{google:instantExtendedEnabledParameter}{google:omniboxStartMarginParameter}ie={inputEncoding}

"which is user configurable"

The vast majority of Chrome's users have no idea what any of those terms even mean, or what the tracking actually entails. Most people don't read EULAs and will never touch program defaults. They certainly don't fully understand the compromises they are making with their privacy. Having these options available is irrelevant for most people.

Out of curiousity... Are all those options in Chromium too?

Does anyone know for certain what differences between Chromium and the closed-source Chrome is?

I find it very hard to trust a browser from the internet's biggest user-tracking- and ad-agency.

These are the only options you can modify from the assigned UI for it (chrome://config). As far as I know, Chrome is the branded version of Chromium. Chromium development is done by open source contributions, but mostly they are on the Google payroll. What do they get from this? As you said: user-tracking so they can deliver even more targeted advertisements. It is great they also deliver a FOSS-ish browser, but there is only a small minority actually using Chromium. The majority gets to use Chrome which, due to Google branding, is vastly more popular.

Their search engine also greatly benefits from all the data hoarded.