I have a post office shop and Scenerio D and A are basically the same. I haven't seen any guidelines labeled "D". How is "D" different?
Also, tips I can have to not look suspicious? There is a lot of things they want answers to, and this post office does not have a long wait time (from my experience), since it's the annex, and not the main.
Scenario D is Scenario A - It's simply being done an additional time for this round.
Don't worry about looking suspicious. If you need extra time to look around, then write your addresses on the package while you're in the lobby, glancing at the available forms, and check out the signage as you approach and are at the counter.
Yes, I agree with elcartev68...walk in slowly, take a look, maybe weigh your package if they have a separate weigh station. Look "lost", pretend you're interested in the ReadyPost items for a birthday package to send next week. Check tickets by 'looking for' a hold mail ticket for the vacation you are going on, etc. I know it can be awkward, but you will get used to it.