I already worked with Shopware 6 and created a couple of apps. I published some of them in the store and some not. Here you can find some of my apps that I published in the Shopware Store:

Popular Apps:

• Free Shipping Hint
• Newsletter in Footer
• Show complete text on product sites

CMS-Apps:

• CMS-Layout Blocks
• CMS-Product Slider Layouts
• CMS Responsive Image Slider
• CMS Block with border animation

Now if you want to create your own Shopware Apps or Plugins, I also wrote some articles about it already. You can find some of those blog posts right here:

• Shopware Custom Fields
• CMS Block in the App-System
• Creating a CMS-Element
• Creating a CMS-Block

There are also a couple of apps and plugins which are not published in the Shopware Store. You can find a lot of them on my github profile

• Real world CMS
• Product Box Quantity
• Copyright Change