i don't think there's a problem even for a non-modular psu, example like mine but still can manage the cables quite good (not as good as modular's of course)

even my CM690 case had a flat side panel but still can cramp all the sleeved cables but a bit harder to close it.

it takes time to manage it all by your own but surely wif few tries u'll get the hang of it

it won't, the black sleeves are meant for protecting the cables. jz don't force against it with sharp edges