You can choose between 6 card sizes - from very small to large.
Each size shows different level of detail for a given item.
If you care less about items details and more about the total number of items - choose the smaller card sizes.
If you need to get better idea of what each item is about - choose the bigger sizes.
The green progress bar in a feature card shows the number of stories done vs the number of all stories assigned to this feature.
The green progress bar in a story/bug card shows the number of tasks done vs the number of all tasks assigned to this story/bug.