Greetings, i understand that this is a question which is quite broad in scope. So answers that address a part of the question can hopefully be allowed. I am mainly trying to get an insight into the proportion and various ranks of officers into

1. A Roman legion ( pre and post Marion reforms republic and later empire )
2. A batallion during the Napoleonic wars - be it French or British. Of course I d welcome cavalry related answers but Guards and Line infantry is what I am looking at

And bonus question if I can get an answer to it : what about medieval warfare where it seems to me that generally the lords would lead their armies individually