"In the loading screen it says fortifications are affected by the proximity of enemy armies on adjacent tiles. It doesn't say HOW though. Does keeping an army next to an enemy capital reduce fortifications (like a siege) or increase them (giving them chance to reinforce)? Either way I haven't noticed the impact in gameplay."
I believe that refers to the "entrenchment" bonus. Which is how many bonus troops gained when fighting on that territory. a 100% entrenchment gives you double the troops you have there (so if you had 5 troopers, you get 10 when attacked)
Im not sure if there's a distinct equation for how much is impacted by your actions. But surrounding an enemy capital on all sides before attacking it lessens the bonus, whereas rushing it from the waterfront means it'll have a much higher one.
"There isn't any visible mechanic that accounts for the fact you can just sit in chapter 1 gaining resources for chapter 2 and so on. The whole chaptering system is pretty weird actually so I'm hoping Custom Campaign doesn't use it and you just don't have a chapter 2/3."
In chapter 1 you're hardcapped to 50 and 30 respectively. Go over that and it gets stolen. Chapter 2 does admittedly let you research everything. But to be fair, unless you're rushing hardcore you're capable of researching the only important things before chapter 3 regardless of how fast you do chapter 2.
"Some of the maps gave massive advantages to the defender in the RTS portion. Mechanically I quite liked this but it wasn't obvious in the campaign when this was going to happen and I don't think it was represented in auto resolve."
Im not really sure what you mean. Are you talking about the entrenchment bonus (which is shown on the world map, and then on the resolve screen)or something else?
"The buildings were a bit weird. The Tavern and Wizards Tower were pretty clear (though the Wizards tower was rubbish) but I was never clear which cards the others provided. It would also have been nice if I could build fortifications rather than have them jut sort of happen. This might have been a good place to sort research out as well, rather than just having regions provide research they could have just provided more spaces to build research buildings. If the research buildings were powerful enough this would add an extra dynamic to the campaign map as well as intrinsically add an element of diminishing returns."
You can sort your cards to see exactly what each type looks like. In short, diplomacy cards boost population, gold, give you sales on units, immunize you to attack, and other type of world map stuff. The other type of card (subterfuge?) are things like causing enemies to not be able to move on a turn, or making them weaker for the purpose of rts combat. You also can choose what to build. Any empty territory, right click and select the build option. You can also sell most buildings if you have no need of what they give.
"Generals seemed to be consistently overpriced compared to their impact on the field."
Their prices go up as you get further into the campaign/hold more territory. At the very start they cost like 8 gold and can add 30% to an auto resolve score. Keep in mind what their stats do. For example, scarlett will add more than henry if you're on the defensive, and fielding only troopers and grenadiers.
"In the preview I heard mention there were different dragon types for people who were more interested in the RTS portion or the arcade portion of the game. This didn't seem to materialise which is a shame. It might have caused some balance issues to have a dragon that was 75% more resilient and regenerated energy 33% faster at a cost of making your troops 25% less effective but I think the single player could handle a little imbalance."
The dragons do have their differences (in starting skills, and how quickly they overheat vs how much damage their fireballs do) however there are unfortunately no differences to how they work off the rts map (at least as far as I noticed)
