You might also find this HL7 benchmark post by @Mark Bolinsky useful, specifically the section titled "Disk Configuration", and the related "Table 2" there.
For convenience I'm pasting this table here (but read the original post for the full context, for example your scenario sounds more like the "T2 Workload" described there, rather than the "T4" one) -
Table 2: Disk Requirement per inbound HL7 T4 Message
| Contributor | Data Requirement |
|---|---|
| Segment Data | 4.5 KB |
| HL7 Message Object | 2 KB |
| Message Header | 1.0 KB |
| Routing Rule Log | 0.5 KB |
| Transaction Journals | 42 KB |
| Total | 50 KB |
This might not be exactly what you’re looking for, as it requires an actual working interface to perform the estimation, and not just a "concept/design" of the interface, but worth checking it out. It indeed takes into account for example also the Event Log, as well as Journals which you didn't mention above but might be important for you as well.
https://community.intersystems.com/post/ensemble-interfaces-disk-space-u...
See Cloud Storage APIs and Cloud Storage Adapters.
See also this example by @Keren Skubach (it uses Azure and not AWS, but the principal is the same).