So, there's no need to customize OAI-PMH settings unless you find its default settings to be insufficient. I get the sense that most institutions leave OAI-PMH settings them as-is, except they might tweak the metadata "crosswalks" if they have added custom
metadata fields that they want displayed different in OAI-PMH.
The "Projects" you refer to in the OAI-PMH 2.0 docs are for more complex scenarios, specifically OpenAIRE or DRIVER (which no longer exists):
https://wiki.duraspace.org/display/DSDOC5x/OAI+2.0+Server#OAI2.0Server-WhyOAI2.0?
Some external projects like these require very specific metadata fields to be available in OAI-PMH, so OAI 2.0 provides a way to configure those separately from your default OAI configs. These projects end up displayed as separate "contexts" in OAI-PMH. See
for example the demo site:
http://demo.dspace.org/oai/
Again though, all of this is usually not necessary to touch or customize. The default settings often work perfectly fine. If you have a more advanced use case though, you are welcome to describe it on this list (or on the Tech Support list, dspace-tech), and
we can give you more specific advice.