The basic army composition in 1100 and 1400 for medieval europe would, for example, be pretty much the same. Heavy knights as the professional striking force, levied or less wealthy men at arms as the foot, a focus on siege warfare. The difference is that armor got heavier and better, and weapons adapted to deal with heavier and better armor.
Depends on which region of Europe you are talking about. Highland Scotland and Ireland might have the same basic army composition in 1100 and 1400 (but wouldn't fit your description of what warfare looked like), but the armies of France, ENgland and the HRE
was different in 1400 compared to 1100. That's the very reason some people (me included) are calling for late game DLC for vanilla, a system that properly represents 12th century warfare cannot also be used to represent 15th and 16th century warfare, without being so abstracted it fits 1th and 19th century warfare as well.
To sum the differences up, armor in the 12th century was maille, which is not as balanced with plate as popular culture and fantasy would have you believe. A suit of maille that covers the entire body is heavier than a full suit of 15th century plate, less protective and more expensive (because it takes longer to make). The advantages of maille over plate is that it doesn't require as much technological/metallurgic infrastructure and knowhow and that it is much quieter than plate.
However, to sum up the differences in French and German warfare between 1100 and 1400, the 12th century had the type of armies represented in CK2 and ASoIaF, the core of the army was a landed warrior elite and the small household retinues of high nobility that fought the same way (in the field of history these are called "Men-at-Arms", but popular culture calls them knights and uses men-at-arms for a different thing*), this core would be supported by militia levies and possibly a few sellswords.
By the 15th century, not only was gunpowder (in form of both handgonnes and cannons) ubiquitous in the French and German armies, but the way troops were raised was to a large extent different. In the mounted and highly armoured core of men-at-arms there were fewer of the lowest nobility, their role mostly replaced by commoner men-at-arms serving in the retinue of hig nobility. The levies of peasants were replaced by better drilled town miltias, the 15h century saw no French, German or Italian ruler arming their peasantry for use on the battlefield (the only role untrained peasants had in warfare was as foragers, harvester, builders and laborers), instead the larger towns were expected to either supply a militia that had regularly drilled and trained in warfare, or money in the form of a war tax to hire mercenary companies (in Italy the
Condotta "Companies" were not really companies as much as complete armies, while in France and the HRE the mercenary companies were legit companies).
By the second half of the 15th century (it started in the 1440's in France), some of the "retinues" of independent rulers were far larger than they had been before. For example, the standing Ordonnance Companies of the King of France (i.e. his retinue) was larger than entire
armies fielded by the Hohenstaufen emperors during the 13th century.
A last example of what 15th century armies looked like, during the Hussite war Regensburg supplied troops to fight the Hussites, what they supplied was not 200 light infantry and 50 pikemen, but:
73 Horsemen, 71 Crossbowmen, 16 Handgonners and 6 cannons. And that's generally what true of warfare Europe during the Late Middle Ages (i.e. from ca. 1350 to ca. 1500), not a
single conscript to be found among the armies of France, Italy and the HRE. It's all men-at-arms, mercenaries and drilled town militias.