\common\buildings\00_CastleCulture.txt
I've checked the wiki numbers on the Retinues page against the text file, and they're the same when it comes to the "starter" bonuses.
\common\retinue_subunits\00_retinue_subunits.txt
http://www.ckiiwiki.com/Retinues
If you combine the data about the "starter" bonuses with the maxed-out cultural buildings in the capital holding, you get the following (ignoring "generic" retinues).
Note that the data is displayed as: zero buildings / first building / second building / third building / fourth building. The cumulative figure is calculated.
Longbow -- Welsh and English
+20% / +35% / +50% / +65% / +80% Archers Offensive
+10% Archers Defensive
Schiltron -- Scottish
+20% Pikemen Offensive
+40% / +55% / +70% / +85% / +100% Pikemen Defensive
+20% Pikemen Morale
Baltic Warrior -- Baltic group and Finno-Ugric group
+30% / +45% / +60% / +75% / +90% Heavy Infantry Defensive
+10% Heavy Infantry Morale
Horse Archer --- Altaic group and Iranian group
+20% / +30% / +40% / +50% / +60 Horse Archers Offensive
+12% / +17% / +22% / +27% / +32% Horse Archers Morale
Knight -- French, German, Occitan, Norman, and Breton
+10% / +25% / +40% / +55% / +70% Heavy Cavalry Offensive
+10% Heavy Cavalry Defensive
+20% Heavy Cavalry Morale
Caballero -- Iberian group
+20% / +35% / +50% / +65% / +80% Light Cavalry Offensive
+20% Light Cavalry Morale
Pike -- Italian
+20% Pikemen Offensive
+20% Pikemen Defensive
+40% / +55% / +70% / +85% / +100% Pikemen Morale
Druzhina -- Russian
+10% Heavy Infantry Offensive
+50% / +65% / +80% / +95% / +110% Heavy Infantry Defensive
+20% Heavy Infantry Morale
Housecarl -- North Germanic group and Saxon
+40% / +55% / +70% / +85% / +100% Heavy Infantry Offensive
+20% Heavy Infantry Morale
Hussar -- Hungarian and West Slavic group
+60% / +75% / +90% / +105% / +120% Light Cavalry Defensive
+20% Light Cavalry Morale
Camel Warrior -- Bedouin, Egyptian, Levantine
+20% Camel Cavalry Offensive
+20% / +35% / +50% / +65% / +80% Camel Cavalry Defensive
+20% Camel Cavalry Morale
Andalusian Cavalry -- Andalusian
+20% / +30% / +40% / +50% / +60% Light Cavalry Offensive
+40% / +50% / +60% / +70% / +80% Light Cavalry Defensive
+20% / +30% / +40% / +50% / +60% Light Cavalry Morale
Berber Cavalry -- Maghreb
+50% / +60% / +70% / +80% / +90% Light Cavalry Offensive
+0% / +10% / +20% / +30% / +40% Light Cavalry Defensive
+30% / +40% / +50% / +60% / +70% Light Cavalry Morale
Cataphract -- Byzantine group
+10% / 17.5% / 25% / 32.5% / 40% Heavy Cavalry Offensive
+10% Heavy Cavalry Defensive
+20% Heavy Cavalry Morale
+0% / +7.5% / 15% / 22.5% / 30% Horse Archer Offensive
Gallowglass -- Irish
+40% / +55% / +70% / +85% / +100% Heavy Infantry Defensive
+20% Heavy Infantry Morale
Ethiopian Skirmisher -- Ethiopian
+50% / +65% / +80% / +95% / +110% Light Infantry Offensive
+30% Light Infantry Defensive
Somali Skirmisher -- Somali
+40% Light Infantry Offensive
+40% / +55% / +70% / +85% / +100% Light Infantry Defensive
Free Warrior -- West African group
+60% / +75% / +90% / +105% / +120% Light Infantry Offensive
+10% Light Infantry Defensive
+10% Light Infantry Morale
Gusar -- South Slavic group
+10% / 17.5% / 25% / 32.5% / 40% Heavy Cavalry Defensive
+10% Heavy Cavalry Morale
+20% Light Cavalry Offensive
+20% / +27.5% / 35% / 42.5% / 50% Light Cavalry Defensive
Goedendag Militia -- Dutch
+30% / +37.5% / 45% / 52.5% / 60% Pikemen Offensive
+20% Pikemen Defensive
+10% Pikemen Morale
+20% / +27.5% / 35% / 42.5% / 50% Light Infantry Offensive
+20% Light Infantry Defensive
+10% Light Infantry Morale
Jaguar Warrior -- Nahua
+20% Heavy Infantry Offensive
+10% / +25% / +40% / +55% / +70% Heavy Infantry Morale
+40% Light Infantry Offensive
+20% Light Infantry Morale
Bar Kochba Guards -- Israelite
+20% Heavy Infantry Defensive
+10% / +25% / +40% / +55% / +70% Heavy Infantry Morale
Steel Bow Infantry -- Indo-Aryan group and Dravidian group
+10% Archers Offensive
+30% Archers Defensive
+15% / +20% / +25% / +30% War Elephants Offensive
+0% / +10% / +20% / +30% War Elephants Defensive
Nubian Archers -- Nubian
+20% Archers Offensive
+20% / +35% / +50% / +65% / +80% Archers Defensive
Frankish Heavy Infantry -- Frankish
+20% / +35% / +50% / +65% / +80% Heavy Infantry Offensive
+10% Heavy Infantry Defensive
+10% Heavy Infantry Morale
Lombard Heavy Infantry -- Lombard
+10% / +25% / +40% / +55% / +70% Heavy Infantry Offensive
+10% Heavy Infantry Morale
Suebi Longspearman -- Suebi
+30% Light Infantry Defensive
+20% / +27.5% / 35% / 42.5% / 50% Light Infantry Morale
+30% Pikemen Defensive
+20% / +27.5% / 35% / 42.5% / 50% Pikemen Morale
Pictish Raiders -- Pictish ("
because one day, lads, you will all be Schiltron")
+30% Light Infantry Offense
+10% Light Infantry Defense
+20% / +35% / +50% / +65% / +80% Light Infantry Morale
+10% Archer Offense
+10% Archer Morale