I use ultralight nylon or silnylon bags from whoever is cheapest for the things you pointed out.
As 805 mentioned you loose pack density super fast when you use too many bags for storage, especially larger bags. A tight easy carrying pack is way easier to achieve when you've got soft stuff loose to fill all the gaps with.
Stuff I keep in ultralight nylon bags: kill kit, first aid kit, food bag, blackpowder gear if I'm packing in a smokepole ....otherwise it goes in ziplocks or mostly doesn't get bagged at all.
Big bags of crap just don't fill the backpack as neatly as small squishy items.
