You can customize sub-channels to have the same display as the main channel.
To do so, go to Online Store on the application navigation and then click Store Settings on the left navigation. You are now on the page where you can edit settings such as Store Name, URL, etc. By clicking the Is Sub Channel button on the right part of the screen, you assign the channel you are currently on to be a sub-channel of another one.
You can also use the Select Parent box, to choose from which store the sub-channel will inherit the logo and theme from, Allow Sub Channel Customization, which leaves the option of further editing open, and select or leave the optional settings of Always use Parent Hero and Always use Parent Overview unchecked, inheriting the Hero and Overview from the Parent Channel.
This will make both the main and sub-channels look and feel very similar or the same, depending on your choosing.