disk-image and partitions

[rendaw <7e9wc56emjakcm@s.rendaw.me>]

I think I'd like to use disk-image but a number of things were unclear
from the documentation:

1. What and how many partitions are created?

Reading the -t parameter I assume it's an image with just 1 root
partition. If I need UEFI will an efi partition be created?

2. How can I refer to the created partitions in the config?

Digging through the source it seems that in some modes of operation the
root partition is automatically created and there's a local uuid value
that's generated and shared between the partition + filesystem config,
but I didn't see that exposed anywhere.

I have various additional storage attached so I can't guarantee device
order (sda/sdb/sdc).

Thanks!