I just can give a half answer:

New factions (no guarentee that the list is complete):
EARLY:

Armenia
Bohemia
Cuman
Genua
Irish
Kiev
Lituania
Norwegians
Portugal
Scots
Serbia
Sweden
Venetians
Volga-Bulgars

Papacy, Nowgorod are playable
Italy is removed

In other eras:

Crusader states
Teutonic order
Bulgaria

New units: a lot

There are also some new provinces (provinces are divided)
Poland -> greater and lesser Poland
Livonia -> Livonia & Estonia
Kiev-> Kiev & Levidia
Chazar -> Chazar and Lesser Chazar
Sweden -> Sweden & Scania

Golde Horde is playable

Just read the thread in the mod section.


IMO, XL-mod is in general much better than the unmodded game, I never played the unmodded game again, when I had unstalled XL.