No, regarding breaking encryption, it can definitely be used. Algorithms to do that already exist. We are missing a large enough computer for that to be feasible, but once it’s available everything which is encrypted with a non quantum safe algorithm can be decrypted.

Luckily they already developed encryption algorithms which should not be broken by quantum computers.

Regarding the working of the computer, yes you can see it a bit as rather than having a bit on or off you can have intermediate values as well. However qbits can also be “linked” to each other. As such you don’t really work on individual qbits but rather on the overall state of the system: changing one qbit will change the value of other ones as well.

Then also you have to be careful about measurement: if you want to read the result you’ll have to measure the qbits, doing that will change the state of the system and you have to account for that.

However, I’m not an expert in quantum computers. I have not studied them or worked on them. Most I know is from bar talks with physicists.