Sylvan versus the Mountain Folk, as well as Sylvan against Dungeon.

Wingael is essentially a cheater; he needs to be developed in such a way as to quickly rush the opponent. This is usually done through attack and leadership, with tactics, a speed aura, and retribution, to reduce the opponent's army as much as possible from the first turn. Additionally, light and luck can be used.
If resilient dwarves are harder to defeat, there shouldn't be major problems with the poorly defended and small army of the Dungeon, if you take more resistance, and luckily there are unicorns and artifacts against chaos, if any are found. Against darkness, Leto will have light.
Against Svea, it doesn't make sense to take a lot of resistance; in any case, her lightning spells are not deflected, but a ring against lightning would be useful.
Erling and Karli specialize in archers; mass evasion would be helpful, and he also needs to quickly break the cart so that the crossbowmen run out of ammunition.