Dry suit is key...
I think the dry suit is key to lightweight overnighters, I will definitely be purchasing one for next season in California. I have just started exploring the Sierra multiday runs, but I know veterans of these runs who agree that a drysuit is a very efficient purchase for multiday trips. When your done for the day you wear your fuzzy union suit around which is hopefully still dry, and perhaps add a stocking cap or a compressable down jacket for extra warmth. Also if you know there will be ample dry firewood--and conditions permit a fire--then this greatly reduces the need to bring warm clothing, which is much heavier than you think since it usually requires an extra dry bag and too many dry bags can bog you down.
Try the old school, foam sleeping pads and cut them down to a size that will support only your back. Then stuff it in your boat sans dry bag. Roll up a section of lightweight drop cloth, used for painting, inside your sleeping bag. If your foam pad is still wet at bedtime use the drop cloth on top of it. Otherwise vice versa. I think it's wildwasser that makes a nice dry/float bag that is perfect for stuffing a sleeping bag into and it distributes the weight throughout your stern better. At night said dry/float bag makes a fine pillow. You will learn to ignore the chipmunks, mice and groundhogs that creep around your head at night.
I stick with meals of high calorie, dry foods: beef jerky, sausauge, cliff bars, tortillas etc. I keep a tube of compressible peanut butter in my life jacket pocket so that I can squeeze down some PB goodness for energy along the way.
For drink: the water bottle purifiers are the bomb for California or other places with good water quality. For spirits, purchase a nalgene canteen and fill it full of Jagermeister. When your done with it you can roll it up and stash it away nicely.
These are my recommendations after a season of packing way to much crap; on one such trip some Colorado and Virginia boaters took advantage of my excessive provisions and everyone gladly pillaged my food and Jagermeister, in regards to my safety, as my boat needed a wheelie bar through the class Vs.
Packing your boat for overnighters is a learning experience and the only way to figure out what works best is to go out and do a bunch of them.