With no numbers shown IG with S&H, it's not possible to get super specific.
Critter perception from least to greatest is humanoid>animals>undead. I've determined that level plays a role, but 3x in S&H is more than enough to allow a level 60 character to run around town during a capped invasion without too much risk (though I wouldn't suggest staying in a room with 10+ capped critters trying to sniff you out at that level).
My rogue has always been 3x in S&H, has had 2 ranks in Armor Stealth since it became a thing. By level 40 undead were able to sniff him out of hiding with roughly the same frequency I see an open role with SMR (which leads me to believe searching out hidden characters is an open role), by the time he was in the dungeon of the Keep (50ish) it was rare for him to get sniffed out by anything at all.
The Ranger (2x S&H, fully spelled up, no blessing lore until level 72ish) was still getting sniffed out by undead occasionally in her 50s and rarely by the time she stopped hunting the Citadel in her late 60's. She's level 75 atm, so I don't have experience above that yet... but against like level foes, she's absolutely on par with where the rogue was at that level. Against foes 20+ levels above her, I'm sure undead would be able to find her sometimes... but I'd be surprised if humanoid foes managed to find her.
I should prolly also note that both characters are in the shadows when they move around hunting grounds, though the ranger pops in and out of them with each attack since she fixskilled into OHE/shield... and she can also take a hit a heck of a lot better than the rogue if she has to.