Hello @mack87-dash and welcome on Linux !
All themes you are installing and the embedded ones are located in a directory made for them :
/usr/share/themes/
You can list all content of this folder with ls /usr/share/themes/
To remove one of them, just run sudo rm /usr/share/themes/<theme folder name> like rm /usr/share/themes/Orchis-compact (it's case sensitive)
I just downloaded your theme and have noticed this message :
You can fix it installing this icon theme - a install.sh is available here or, you can use your theme with a other icons theme this way :
I have took a other theme, and only took the decorations and controls of a other theme.
Good usage of linux 