Sorry, I haven't used CloudDrive nearly enough to be able to tell you whether your plan is actually sound (I use DrivePool and Scanner a lot more) though that may change in the near-ish future.
"Drive Usage set to B only having duplicate files." - Have you tested that this works with a pair of local pools? If so, it should also work with a local+cloud pool pairing.
"Is read striping needed for users of Pool C to always prioritize Pool A resources first?" - According to the manual the answer is no; regardless of whether Read Striping is checked it will not stripe reads between local a