The races you saw on youtube are based on a “third party” software developed by @Der_Bayer, called BROBOT
The game don’t have the feature to see all your car actually race between them.
You can see your cars run a single lap on the “test track” tab when the car is complete, but only one car at the time.
You can see a live race with live commentary this sunday. More info on the BRC thread here below.