I mentioned XL because it's very difficult to fully develop a Castle, and it takes less time for other Castles. Also, due to the cost of units, but it's not a given that enemies will have Ultimate abilities. This is how many monsters, chests, and other modifiers should be on the map so that enemies reach level 30. And even if you play against the computer, it definitely won't reach Ultimate abilities.
You're Sylvan, and as far as I can tell, the light-skinned creatures feel good on any map.