I don't have a ready reference with a description of all the options and their defaults, sorry.
After ExitBootServices, the OS "owns" the platform and can do as it chooses, and it is not constrained by the UEFI restrictions -- it is free to reinitialize the PIC/APIC/LAPIC and MSI/MSI-X and use hardware interrupts as it chooses. The compromises are made solely in the firmware (in the DXE environment, where the firmware's own NIC drivers are in use) and are only relevant prior to ExitBootServices.
I've been contemplating setting the firmware up to use interrupts in a way that is "concealed" from the rest of the DXE environment, so that we can achieve better performance while not visibly breaking the UEFI specification... Haven't actually implemented anything along those lines yet.
Cheers,
--
Darius