Yup. Nothing intrinsic to it that needs checksums.

    zfs set checksum=off rpool

Yes, what's more difficult is implementing data checksumming without CoW. What you may not be used to in ZFS is a nodatacow option (per file or per filesystem) which does exist on Btrfs and it implies nodatasum (no checksums for data, metadata is still always checksummed and cow). Conversely, nodatasum does not imply nodatacow.

Sure, just assume that there's no such thing as bit rot.

I think you're mixing up checksumming and content-addressing.