There is more difference due to word order than just emphasis. Also, it is not only subject-verb inversion.
Consider "how selfish we are." It is not really a complete sentence, but a fragment with something implied in front of it. It could be something like "Look at how selfish we are." That is, "how selfish we are" is a pointer to a quality of us.
This might be used by somebody writing an editorial in a newspaper, with the editor looking down his nose and trying to get people to donate more to the Red Cross or something. "How selfish we are. We can't even donate as much as Shelbyville. Tut tut."
Now consider "How selfish are we?" This is now a complete question. It is asking how much of a particular characteristic we have.
The newspaper editor might use it so. "How selfish are we? Are we as bad as those people from Shelbyville? Are we really going to cancel our donations?"
The two have the same effect, but one is a statement, one a question.
The other one is "How are we selfish?" This is asking for information about the ways in which we are selfish.
The newspaper editor might use it so. "We gave more than Shelbyville. How are we selfish? Compared to them, we are very generous."
Best Answer
That is subject-dependent inversion, which is an information packaging construction where the subject is switched with an internal dependent of the clause.
For your original example, the usual canonical ordering would be something like:
which has Subject-Verb-Dependent order (or S-V-PP order).
With subject-dependent inversion, it becomes:
which has Dependent-Verb-Subject order (or PP-V-S order).
A writer will often use subject-dependent inversion when the subject contains newer info than the info that is contained in the fronted dependent, or when the fronted dependent is a locative expression (e.g. "behind me"). We often prefer to have the newer info at the end of a clause or sentence, and have the older info at the front (which is usually the subject slot). Locative expressions are often moved to the front in order to help set the setting for the rest of the sentence.
You'll find this type of construction more often in edited prose than in informal writing or casual speech, because it usually takes some editing effort to apply this (subject-dependent inversion) to a sentence. Also, there are pragmatic constraints on when this type of inversion is acceptable.
For more info, there's the 2002 CGEL, pages 1385-90, "5 Subject-dependent inversion". For example, starting on page 1386, there's section "5.2 Pragmatic constraints on inversion", and its first paragraph is:
And the discussion on these pragmatic constraints on subject-dependent inversion goes on for another couple of pages.
NOTE: The 2002 CGEL is the 2002 reference grammar by Huddleston and Pullum et al., The Cambridge Grammar of the English Language.