S3 - external versus internal
1) But I have to say, it is logic that internal storage has got better performance than external. Data have to go a longer way with an external storage.
2) Enterprise customers receive additional support. We want to have working ownCloud systems. You need some knowledge about s3, if you want to have it as primary.
3) What do you mean with this question? You can copy/ import data from one storage to another one. The same is with different S3 storages. Is that the solution?