The Tax and Fee is completely dependent on the people owning the village. If they want people out of their village, they put them at 100 gold and 100%. This is especially important if you just took land away in a war or something, to make sure you don't get any ugly surprises.
But this isn't how it is everywhere. Many of the big land owning clans (and even some of the smaller ones) got certain villages with 15-25% tax and 10-25 fee. The best way would be to ask them directly, but you could also figure it out by looking at how many people they have compared to fiefs, how far away they are and how likely there will be other individual players there. The less randomers and the more fief space per player, the more likely they are to have a good deal for randomers. If they don't fill all the spots themselves, it's better to have a randomer pay 15 gold/h to stay there.
Personally, I've set my fief on 25 gold/h and 25% tax, since I don't want too many people around, but I'm not gonna stop you completely. Ofc, that is Ilvia and Ilvia is pretty far off in a corner with mountains and rivers surrounding it. Not many people coming there. Although, I've been thinking of opening it a bit more. Either lowering the tax or the fee. Will have to raise it if too many come flocking to it. Anyone interested in coming here?