Azurewraith
Explorer
The DC is the DC to me skill checks are broken down into 3 skill(Prof) natural aptitude(stat) and luck (dice). As for the drowned being there wouldn't it be a auto success or a int check to rememberSure its possible to narrate anything. But to me denying the drow elf the knowledge that she should have based on her background seems like a more severe invalidation of her choice to be a drow elf from this particular city.
Sure I would have different results even if their (adjusted) roll was the same. Let me sharpen the example: instead of wading through the stream, suppose the PCs are trying to jump across a 5 foot stream with 2 foot high rocks sticking out the stream. Two PCs both have an (adjusted) result of 10. One of the PCs has 16 Str, and the other has 6 Str. I would let the 16 Str PC clear the obstacle, while the 6 Str PC would not. Would you rule that they both succeed (or fail) the same?