can you right click start
choose disk management
expand the following window to show all columns/rows
take a screenshot and show link here. We see what its done.
Win 10 tries to be helpful when installing, if it finds spare space on another drive it will put partitions on it as well. Only way to stop it is only have 1 drive attached when you install win 10.
System partition is the boot partition so its going to be slower than if it was on nvme.