Do I need to create a Board if we have only 2-3 files to review?

This is a great, highly practical question! The decision of whether to use a Board depends less on the quantity of files and more on the context and relationship between those files.

Same Campaign/Project: You should use a Board if the 2–3 files are logically linked by a common goal, customer, or campaign. For example a banner ad, a short video, and a print flyer, all belong to the same marketing campaign or project, putting them on one Board is strongly recommended.

In short, you don’t have to use a Board for just a couple of files, but it becomes necessary if the files are related to the same project or campaign.