MSFS 2020 isn't utlilizing full gpu -cpu(mainly low wattage of gpu)

You can’t look at just the one “overall” CPU percentage. That is the percentage of total core usage, but MSFS does not use multi-cores very well. You can be limited by your main thread and be CPU bound even though many of your other cores are very lightly used. For a better picture, you should check out individual core usage in Task Manager.