Can be both but I also think in Oda's mind characters become much more fragile when they aren't trying to defend themselves. Against Gunko Gaban completely dropped any resistance because of Colon.
I always said that most OP top tiers have normal durability, Kaido and BM were highlighted to be exceptional freaks because of how durable they naturally are. What makes OP characters durable/have high endurance is their haki/willpower