Hi
For the custom pages: In JA Builder you have to create own blocks from the given gallery of the blocks. Please take a look on this documentation.
Als,o you can add the new blocks and customise them from JA Builder that you can say custom blocks with different colours, design.
For the screenshot, you attached it looks something similar to our pre-loaded blocks that give this kind of view. Also, if you would like to add any 3rd party module or a custom HTML module you can use the Spotlight type blocks that gives you the option to divide the blocks in more position and you can publish module in it.
JA Builder has several new design blocks and Pre-built pages that will help you to make the website in very less time.
Let me know if you have any confusion or question in this topic.
Regards