In general YES. Your app is automatically up to date when you make changes from your control panel, without any new app submission process.
The only things you can’t modify on your apps without a new submission are app icon, app startup image (splash screen), app name, app description, categories and keywords (which are submitted to App Store and Play Store), and mobile website url. If you add the Places/Directory feature while your app is already published, it will not work and your app will need to be republished. Another point concerns the “Audio” and “Radio“features, if you want them to work with multitasking (navigate through your phone, outside your app, with music keep on playing), you have to integrate them on your first publishing, if your app is already published when you add these features, they won’t work in multitasking mode, and you will have to submit it again.
Design, logo (not app icon, just the logo in the news wall feature), colors and of course features are editable whenever you want and as many times as you need.
A new submission process due to your mistake/omission for example because you want to change the app icon, splash screen, or if you want to add multitasking on “Audio” and “Radio” feature, will cost you $69 for both iOS and Android or $49 for iOS only and $29 for Android only.