It may be your bucket, but Amazon is still a third party. Does turning off logs disable all logging on the Amazon side, or just your copy of those logs?
You really think Amazon doesn't have logs for security and troubleshooting?
What about all the networks between you and Amazon?
IANAL but I think you still need to sign a data processing agreement with them and have your users confirm that they'll have access to their data.
Does Amazon do unreasonable things with your users' data? Because otherwise you wouldn't need consent.
The terms are broad in GDPR, so you need the DPA just for Amazon to store it, as that's "processing". However, you don't need your users to confirm that, they agree to share the information with you (controller) and you'll have some sort of terms in your privacy policy allowing you to share personal information with 3rd parties you regularly interact with for legitimate purposes who will be bound by the terms set forth in your own privacy policy.
No, you still need a processing agreement with Amazon, but that's not a problem.
your own bucket wouldn't benefit from browser url-based caching of common assets (libraries, fonts, etc)