Well, I definitely wouldn't call myself an expert using this tool yet, but I'll give you my opinion on the topic. As with most questions like this, the answer is that it depends. I'll go over a few decisions we had to make when settling on a modeling strategy. We still don't have everything ironed out.
Originally, we tried to put all of our stages and tables into one model. This turned out to be cumbersome when it came to opening and saving the project. It was pretty slow to load that much data and slower to save it. We broke that into one project per stage (we have 3), which alleviated this problem for now. The upside to this is that we can see all of the tables for any stage all at once. The downside is that when anyone needs to make a change, they need to copy the entire stage, then create a subview for the changes. Once this goes to production, the original golden copy needs to be updated.
We chose this path because our model doesn't have islands of data. Everything is connected in one way or another. If we had tables that were clustered and the clusters are not tied to one another, I would create a separate project for each cluster of tables.