I did some experimenting and documented my observations about how Crostini runs on my Pixelbook. For people concerned about the performance impact of Crostini running on a Chromebook, I note that the virtual machine and any containers within do not automatically start on boot and therefore the cleanest way to run is to not launch the Linux Terminal app, which you see when you enable the Linux apps beta on Chrome OS.

The first time you launch the Terminal app the virtual machine (termina) and default container (penguin) start, which accounts for the longer than perhaps expected time to launch.