I'm crawling through the second mission, and it feels a bit bland.

I didn't like the second mission in the second half; after defeating the elves, the map became a tedious search for upgrades and dwarves hiding in their castles.
However, the war against the elves was quite enjoyable.

In terms of functionality. I didn't fight with peasants, so I'll skip that. Archers – two arrows, slightly higher initiative, very strong under Waren. Perhaps not the best choice with other heroes. The armored infantry are very similar to their "white" counterparts; the difference is insignificant. Griffons – limited usefulness, a ridiculous creature. Its ridiculousness can be compared to Megara performing "strike from the sky" and receiving a counterattack. Monks – simply supermen. Of all the possible upgrades, I would only choose them. Cavalry – an improved version of the "red" ones, use is a matter of preference and depends on the situation. I liked the angels, if only because they duplicate all light magic (analogous to the light unicorn).

Archers are a great unit... The total damage is good + one of the archers goes first.
The griffons' stun often works. The only thing they need is boots with +1 speed so that they can kick someone on their first turn.
Although sometimes royal or assault griffons are more useful because of their flight.
The computer doesn't really use light magic... what's the point of the duplicate? When playing against a player, yes. Against the computer, you're casting mass light spells anyway (if you're playing light, and if you're playing dark, it's a useless ability).
The knights are weak – zealots can easily defeat them.