I Have tried it to have the same shell theme, icon theme and plank.
applying shell-theme was not successful but icon theme and plank are ok.
Install user-themes gnome-shell-extension as system-wide.
Install shell-theme and icon-theme also as system-wide.
First we need to compile the schemas for admin user as how we want it. In your case
below is an example,
# Custom Settings for ADMIN ACCOUNT which will be used for standard users too
[org.gnome.shell]
enabled-extensions = ['user-theme@gnome-shell-extensions.gcampax.github.com']
[org.gnome.shell.extensions.user-theme]
name = 'Mojave-dark'
[org.gnome.desktop.interface]
icon-theme = 'Mojave-CT-Classic'
create a text file with above content and name it as 99_ADMIN_SETTINGS.gschema.override
move the above file to /usr/share/glib-2.0/schemas/
and then compile the schemas with below command
sudo glib-compile-schemas /usr/share/glib-2.0/schemas/
You can edit the above file with any gsetting keys you wish at any time.
Any changes you made to above file, you need to compile the schemas.
At anytime you wish to have default values.. simply delete the file 99_ADMIN_SETTINGS.gschema.override
and compile the schemas.
For plank.. copy the .desktop file of plank from /usr/share/applications
to /etc/xdg/autostart
with below command.
sudo cp /usr/share/applciations/plank.desktop /etc/xdg/autostart/
Tested in gnome-shell 3.36.6