Welcome to the forum!
This shouldn’t matter. Storage v1, v2, and Blob Storage all worked for me in the past.
This depends. Hot storage has higher cost for the amount of data you’re storing, but lower transactional cost. Cool storage has lower cost for the amount of storage, but much higher transactional cost. If you choose Cool then you MAY want to disable certain features of duplicati, like compaction and backend test verification. These two things will download files from the back end storage, and if you’re using Cool storage you’ll incur additional costs.
Cool may be the better choice if you think you’ll rarely have to restore data.
Yeah turn off public access for sure.
Let me know if you have any other questions!