Hi Splat! I've only just rejoined so may well be a bit behind the others in terms of current products, but your concerns are the same as mine so thought I let you know what I use for them.
Dehydration - many swear by Hada Labo. I no longer get on with it (gah, Rosacea!) but it was great for a while. Not moisturising in itself I found but good for boosting the hydration power of whatever you used on top of it.
What I LOVE obviously is the Goodal Waterest First Essence and Lasting Water Oil (more of a serum). They're doing amazing things for my dehydrated, previously cystic-acnefied skin. I've practically ordered it in bulk as I'm so scared of running out! Buy via eBay because the Club Clio shop is expensive.
For 'whitening' or in actual fact brightening and fading scars, I think the Benton Snail Bee serum is great. I mix in a blob of a propolis ampoule too which seems to agree with me. I had a bee venom one by Tosowoong but didn't love it as much, although it's still good. Needed snail!
The Innisfree red wine sleeping pack is still my go-to, despite my well-documented hatred of the smell (I don't like grape scents). So it must be good?! I notice the difference in the morning, I look brighter and fresher after using it.
Love the Beauty of Joseon Dynasty cream too. It supposedly has whitening properties but I can't tell, probably due to all the other whitening stuff I throw at my face. It's just a lovely cream that smells gorgeous and my skin likes. Win!