Hi!
One remark about file sizes: please keep in mind that attachments will get converted to Base64, which increases their size. An image that is 3.75 MB on disk is around 5 MB as Base64.
As far as I know, Bedrock endpoints only handle attachments up to 5 MB (Base64).
About your question around multiple attachments: you can manually ingest multiple attachments to GenAI agents; however, GenAI Connect rules only support single attachment analysis. Check out DocAI with Custom Attachment Lists if you want further details on this and a very interesting workaround by Fergal.