Some areas you cannot see the enemy until you engage them. This is typically the case for non-quest fortresses or strongholds, as you mentioned above (engage at your own risk!).
Graveyards will tell you what kind of enemy you’ll face, but won’t show their strength.
Hope this helps.
"It is not death that a man should fear, but he should fear never beginning to live." ~Marcus Aurelius
Game: "Characters with a height advantage against their opponents are harder to hit"
Me: "That's not true, and my short axeman is living proof!"