What is the difference between the two?
They are both architecture templates, but they are designed for different goals.
The "Balkan Architect Architecture Template - Metric and Imperial" is designed more to be for students and architects that want to have an all-in-one template for competitions, client presentations etc. The families look nice, they look good in renderings and there are many to choose from.
The "Architecture Design Template - Revit 2020" is made for design. It has a minimalist, clean, elegant look and it's meant for use in the initial design stage because it allows you to concentrate only on the layout and the form of the building. It has no families that can influence the style or the feel of the design.
Please take a look at both for a more detailed description.
Note: Both are for Revit 2020 newer versions and include an Imperial and Metric versions.