What is the best water level for a load of clothes??

I do almost the same as you, If it is a small load, then I do a small wash cycle. And I do believe that a medium load would benefit from doing it in large water level, I feel that the clothes will have more room to move around and get a better cleaning. Even when I do a large load, I don't fill the clothes that much because of this. I do have to say that this summer I have been doing wash in cold water, and have had no problems , and they do get clean. But every so often I do the whites with hot and bleach to give them that extra boost. I too have a top loader which I love. So keep doing as your doing, I really don't think it is written in stone Hot or cold or med Large. It is your choice.