With the settings available in Gecko Customizer, you will be able to upload and customize your site logo and site icon ( Favicon). You can find these settings in WP Admin -> Gecko -> Gecko Customizer -> Site -> Logo Section.
Logo Image section:
Here you will find settings to upload logos separately for desktop and mobile devices, favicon also.
Tagline section:
Other section:
If you want to change the color of tagline text and logo text you can change it in WP Admin -> Gecko -> Gecko Customizer ->Theme -> Header -> Header colors section settings.