- It is a sandbox type campaign with no real storyline. As far as quests are concerned, you have two "books" : one correspond to your selected victory conditions (you can pick them at the start of the game : from holding 10 to all provinces, getting one hero to level 20, maxing out your faith, etc ...), the other is basically one book (like in the vanilla game) full of major quests. Those quests include various major objectives (like beating that pesky upstart Arthur, killing the Sidhe leaders, etc ...), major heroes recruitement quests (including both new heroes, like the Welsh Druids and the Saxon Sons of Beowulf, and old signature heroes of the vanilla game,for example the Druids have quests to recruit Merlin, Caradoc, etc ...), artifact-set quests and quests that allow the recruitment (or combat summoning) of the faction's big unit (Angelic Guardians for Saxons, Dragons for Druis)
Plus, you have a lot of random, ?-type, quests : some old, many new and unique to the expansions.
However note that all of these quests, including the "book" ones, are either battle, diplomacy, or merchant type quests. There are no text "choose your adventure" quests.
- The diplomacy is expanded a lot from the base game. It is divided in 4 sections :
- Kings : your rival kings
- Wives : a choice of 4 potential brides for your ruler, each one bringing different advantages (including unique units) to your realm
- Knights : a lot of (more or less generic) "knights for hire"
- Other : the 4 misc factions : the Sidhe, the Bishops, the Outlaws, the Marauders
For brides, knights and other factions, it is basically about bribing them with different type of gifts to improve your reputation (most diplo actions have a cooldown, so you must raise your reputation slowly over time), until your reputation is high enough to marry the bride/recruit the knight.
The Outlaws can, provided your reputation is high enough, do spy-like actions for you (like poisoning enemy supplies, incite a rebellion ...), or you can pay them protection money so that AI kings can not use them against you (they can, and will take the oppportunity). The Marauders can brew trouble in other province (with an hostile army), or provide you with viking/orkney type troops. The bishops can sell you christian artifacts, christian troops and heroes. Same for the Sidhe, plus they can attack enemy provinces bordering Bedegraine. All of those diplomatic actions have, of course, a cost and a cooldown.
The diplomacy with the other kings is a bit more complicated, because it involves 3 different gauges : reputation is the one you can increase with gifts and treaties (or decrease with war or bad actions), and will also vary with the difference in faith and morality between you and the other king, fear is based on your power (land, troops) compared to the other king's power, and peacefulness is based on "opportunity" factors like for example if you have unprotected provinces adjacent to the enemy's.
Depending on the value of those gauges, you have a variety of diplomatic options, like trade contracts, millitary passage, alliance, up to vassalization and even integration in your kingdom.
To answer your question, of course you can "game" the system, but, for example, you cannot vassalize or absorb another kingdom by bribes and money alone, you must also make sure the other king fears you (by mustering a large army and owning a lot of provinces).
- The other kingdoms don't seem to cheat or spawn massive stacks out of thin air. OTOH, quest objectives are linked to battle of appropriate difficulty. I'd say that the expansions are balanced, and overall a bit easier than the vanilla game, not because of poor AI or imbalances, but because of the fact that you can pretty much go at your own pace and set your own objectives, there are no quest triggered events to turn your realm upside down or other unforeseen consequences of completing the storyline too fast.
- Plus : plenty of stuff, like new heroes, new units, new spells, new skills, new quests, new items/artifacts/sets, more stuff on the morality chart