You can specialize the rules using the ID of each menu.
To target only the primary menu bar use
#nav-primary .genericon-wvrx-menu:before {content:”Menu”;font-size:60%;}
#nav-primary .menu-toggle-button {width:2em;}
To target the extra menu at the top of the content use
#extra-x1 .genericon-wvrx-menu:before {content:”OtherMenu“;font-size:60%;}
#extra-x1 .menu-toggle-button {width:2.5em;}
If the text has the same width in both, you don’t need to specialize the second rule