Not sure which crypts you mean, and wouldn't know if they're open-able anyway. All I know about the Shadowy Catacombs is that the Shadow Warrior starts there. /helpful
The Shadow and Light campaigns are both pretty similar. You fight Gar'Colossus, Octagolamus, a dragon (which dragon depends on the campaign, but it's still a dragon), Carnach, the Fog (Shadow campaign fights the Fog once, Light campaign fights it three times), Garganthropod, the winged demon thing, Facetteleon, and the Nameless Guardians. The motivation for fighting each boss is slightly different.
That's just speaking to the main quest line, of course. Side quests are at least a little different in what's offered (there's a quest in Thylysium that my Shadow characters can take that isn't in the Light campaign, but haven't explored all differences so don't know how extensive those differences are). But if the same quest is offered, both campaigns do the same thing. In other words, if my Light character takes the Kobold Chieftain quest, it will be the same quest as the Kobold Chieftain quest that my Shadow character takes.
In short, I'd say no, they're not very different. My Shadow characters still can't kill NPCs, and still auto-accepts things like the Holdup quest (which makes zero sense to me, let her die, I'm evil and don't care).