B2 is Backblaze’a version of S3. It’s a cloud storage solution. https://www.backblaze.com/cloud-storage/pricing
Restic will encrypt the backup https://restic.readthedocs.io/en/latest/070_encryption.html
And it will backup directly to B2 so not intermediate storage is needed.
For me i keep a local one so if I lose a file or something gets corrupted I can restore locally without any egress costs or network lag. The sync to remote is in case of local data loss for example fire or theft.
Rclone will (should) be faster than doing a restic sync due to not having to do any deduping etc.