I'm asking specifically about France as I know each country had a very different system. Looking at depictions of France in the 13th and 14th centuries it seems like a hodgepodge of different titles having land. Some land is owned by the crown, some land is in duchies, some is in counties, some in viscounties, some is in marches, and its all a mess.
So my main questions are: Was there any difference between a duke, count, viscount or marquis besides the relative rank and prestige? Like, could a duke have counts or viscounts as vassals as they are a lower rank? Or were dukes, counts, etc, just all different types of nobles sworn to just the king? Also, where do baronies come in? Did all of the higher noble ranks generally have them as vassals? Where they similar to the barons in England, who gave some of their lands to knights as knight fees, and had very spread out territories?
Thanks for the help.
The relative hierarchy of titles (duke, marquis, count, etc.) doesn't reflect their respective power. It is indeed more a social rank than a reflective or their power or riches. For example, the Count of Toulouse was a very powerful lord (and one of the original peer). The title "marquis" was only meant to be because the land used to be near the frontier of the country during the Carolingian era. One of the most important lord in the Middle Ages, was just a Lord: Sire de Coucy whose motto was "Not king, not duke, not anything, I'm just the lord of Coucy" (Enguerrand III was the most powerful vassal of the king of France). The title "baron" in France is a low level title in that hierarchy (duke, marquis, count, viscount, baron, lord) with some specific titles here and there ("vidame" which is the military head of a bishop), so it is different from what it means in England. However, "barons" can also be used as a general meaning of all kinds of lords. So if one talks about the "barons of Brittany", it doesn't mean only the holders of the title "baron" but of any noble title.
Of course, dukes had count and viscount as vassals. That's the whole point of that hierarchy. You have to remember that the LAND is where the title is, not the person. That's why one person often had countless titles because they had countless lands. So a land titled a viscounty normally was the fief of a county which in turn was a fief of a duchy.
The big difference with England is that in England, the Normands basically took all the land and had very big domains, chipping some for payments and rewards. In France the dividing of the land had started since the 9th century and reached a very advanced state in the 11th century (the height of fiefdoms). This created an enormous number of lands and titles. Then aristocrats, through inheritance and war, tried to slowly grow their domains: get that viscounty here, that barony there, that lordship there, and try to make it into one continuous holding. This is where the 13th and 14th centuries were at. It was actually the policy of the King of France too, and they succeeded at it pretty well: grow their own domain to make it coincide with the kingdom.