1) I am interested in the building-up-your-lands aspect. How does that feel? Is it satisfying to build a thriving realm out of nothing, can you build infrastructure and medieval forms of industry like mines etc? Does a game in 1400, with more sophisticated infrastructure around, feel different than in 1100?
Well, tech, holdings, and buildings are probably in need of serious balancing. My last game as Novogord-->Rus, Lithuania, et al, saw me research one tech in my capital of Novogorod in 150 years of gameplay. I suspect that research and spread is a bit off.
That being said, buildings are unique by holding, but have some overlap. I'd like to tell you about city and bishop buildings, but I don't even own them long enough to look at their buildings. As for castle holdings, they are either fortifications (walls, gates, arrow slits, etc.), farming related (castle town), or troop related (training grounds, barracks, donjon, keep, etc.). They have interlocking dependencies, so I usually build a wooden palisade first because it unlocks some other things I like. (Yeah, a basic castle does not come equipped with a wooden palisade, so you really are starting at the low end with a new castle.)
There are cultural specific buildings, too. The Norman one is a squire list, which increases heavy cavalry. The Russian one is something I can't remember, but it increases heavy infantry. The heathens have their own. The Baltic pagans, in particular, have special buildings that substantially increase their number light infantry, making them a bit more dangerous than they were in CK1. (Since it's light infantry, a serious force with heavy infantry will generally still plow through them; the Teutonic Twits should have no problem conquering the Baltic pagans.)
Most buildings add either revenue, garrison, fortification level (which is not always tied to garrison size) or levy size. Castles generally have nice fortifications and levies. Also, just like Sengoku, levies that say home add to the garrison of the holding. This can make castles a rather tough nut to crack unless you brought half of Italy with you to the siege.
2) Do buildings have other effects than money and troops or recruitment speed? Like a bonus to technological advance. Or that they appear in certain events. And most importantly, do buildings affect the education of children in that province like they did in CKI? What about schools and universities, do they increase the chance of a more educated and capable child?
I don't know. Tool tips do not list any effects on education or technology. But then again, it wouldn't surprise me if it was running under the hood. Also, since research doesn't seem to be working properly at the moment, I would hesitate to speak on that subject.
Or is it only the guardian? Can you give the child into the care of a foreign ruler, so that he returns talking Italian? And what exactly is the education attribute?
Children may get the culture of their guardian, and even the guardian's religion. This is very important and something to keep in mind, if you don't want an Italian monophysite England.
The guardian of a child reacts to child events, making decisions about the child's traits. You can also give a child to another ruler, but I tend not to do so. I use betrothals to secure peace treaties. (I am wary of anyone educating my direct heirs except for my current ruler; I don't want someone else filling their head with nonsense.)
I have no idea how a child's final education is decided or what influences it. I can have a child educated by a Brilliant Strategist, and they end up as a Dutiful Cleric. Perhaps that is something else that is getting tweaked.
3) Do epidemics other than "the plague", e.g. typhoid, influenza or dysentery spread to other provinces? In CKI they didn't, they stayed in their province. Can characters be infected with them?
Yep. I had consumption tear through my realm this evening, killing courtiers and relatives.
Oh, and attrition in counties with diseases in them is atrocious. And since the diseases spread on the map, it might follow you around and ruin your offensive war.
4) Do you have the impression that women all look rather similar?
Not any more than the men. My screenshots don't show a lot of women on them. Looking at a list of potential brides shows a great variety. And, of course, female portraits age just like male portraits.
Personally, I'll be treating the post-Conquest start date as the "default" Grand Campaign. I'll only start before that if I want to play one of the 3 factions in the conquest.
That's what you should really do if you want a historical outcome. I do that about 50% of the time myself. I don't do it all the time because I either forget or don't care because I'm at the other end of the world.
Also, playing as Harold is a blast. I defeated William within a month the last time, but spent 10 years trying to throw the Norwegians out of York and the northern counties. It was an ugly, vicious war that devastated the countryside.
And then I took out the Welsh to make me feel better.
