Any synthetic or semi-synthetic oil is compatible to mix with a non synthetic oil, so flushing is not an issue if you were to switch between them.
In your location, the 5w-20 is fine. Some folks switch to a 5w-30 in warmer climates, or if they are using the engine for extreme applications.
Many countries in Europe do not sell 5w-20, and vehicles sold there list 5w-30 in the export sold vehicles owners manual for use. 5w-20 is used and suggested in the modern engines today primarily for fuel economy; while we may not notice this with our daily driving, the automotive manufacturers can meet the "fleet MPG requirements" a bit easier that the Federal requirements impose on them.
It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt.