On Iberia, here's the current situation in my current game, the year of which is about 1115:
I am playing as (High) King of Ireland, and married my second son to the Queen of Aragon, and their kid now sits on the throne (this is why I am involved in Iberia in this game). Leon and Castille united (probably because of some family niceties or something), while Aragon has reclaimed a few provinces from the Muslims (but only like, say, 5 or something, which means it only controls a little less than half its de jure territory). For the past decade or so, because of my alliance with Aragon, I have to keep helping it when it goes to war against various Muslims in the area. The causes of the wars are varied: one was a Kingdom-level invasion, another was Aragon claiming a two-state Emirate as its de jure territory, another was a holy war, and so on. I have to say, though, that it was my troops that saved them in a couple of wars when they were fighting against the larger emirates. However, the Muslims also made some territorial gains against Leon-Castille in Gallicia, and I was seriously considering declaring holy war on the large emirate that controlled it to get Gallicia, but then I decided against it.
As a conclusion, I'd say that while the Iberian situation does favor Christians more so than in vanilla, it's not absolute. If anything, at the least in this game, the situation is relatively even, which is what I would prefer, rather than the Christians get wiped out.
(Side note: I did add some game changes based on the changes in Fawr's big mod, although the only one relevant to the results here is the fact that Muslim invasions are only possible if the Muslim aggressor controls territory within the de jure kingdom. I do not think this really changed the situation in Iberia much, given how messy it is and how close everyone is to each other, although I'd just like to add it here in case)
