Hey dont know a guide but..
Soul gems - the higher the creature the better the soul. So easy things like deer, rats, mudcrabs will feel the smaller gems. I think common are creatures like atronachs, fermir, spiders. And grands are the badeset like giants, sabretooth cats, mamoths etc..
Yes bandits have to be trapped in black soul gems because their people. Its because in skyrim there are two different types of souls. Creatures have white souls and People have black souls, hence white and black soul gems.
And im not 100% but i think as your enchantment level goes up, the effect when you dissasemble a weapon goes up. For instance i have not done much, so if i dissasemble say a ring with +20 health regenaration, when i go to use that enchanment on something else, say a necklace i will only be able to enchant with like +15. so when your level goes up i would think that you would be able to takethe full effect and maybe even better at higher levels.