Yes, there are different flavors and there are a few things you can do. First, install
gnome-tweaks so you can easily select different themes and icons:
sudo apt update
sudo apt install gnome-tweaks
Search for "tweaks" in your applications and the app is pretty self explanatory. You can change themes and icons from there.
It's also possible that you have regular gnome shell installed as well as the standard Ubuntu desktop.
If this is the case, you should be able to select one of the two from your login screen before you sign in (look for a gear icon or something to click on that will offer a selection of different desktop environments or flavors).
As for the extra icon for you mounted volumes, you can disable this feature by running the following command:
gsettings set org.gnome.shell.extensions.dash-to-dock show-mounts false
Supposedly, the feature is there to offer easy access to the mounted partition or device and to also provide an easy way to unmount the volume. Also, you can re-enable the feature at any time by running the following command instead:
gsettings set org.gnome.shell.extensions.dash-to-dock show-mounts true
You can read more about the mounted drive issue here on OMG!ubuntu.