I am starting to use annex and feel a bit overwhelmed. I would appreciate guidance on this use case.

1. Content must exist on multiple external drives only. I do not want those files in my internal HDD.
2. Not all drives will have all files. Probably none will. Drives might be smaller than the full set.
3. I should always have two copies of each file somewhere (and be warned if not).
4. Some files already exist in some drives I intend to use annex with in this way. When setting annex in them, I had rather avoid having to transfer in files from another set up drive if those files already exist in the new drive.
5. Some drives will necessarily be using FAT32.
6. I will be adding new content over time.