The systemd configuration for the uwsgi emperor has two issues.

Firstly, there is no systemd-tmpfiles configuration file for the emperor. This makes it more difficult to use a unix socket (rather than a TCP socket) than it needs to be. From what I can tell, it should be as simple as copying the existing tmpfiles config file in the Arch package a 2nd time, with a filename that matches that of the emperor service unit file. My reasoning for this is that the example provided here matches that of the currently available file:
https://github.com/unbit/uwsgi-docs/blob/master/Systemd.rst#putting-sockets-in-run

Secondly, when using the emperor with a unix socket, this message gets spammed into the syslog: "Got notification message from PID 123, but reception only permitted for main PID 456". This issue is described more fully at the following URL:
https://github.com/unbit/uwsgi/issues/797
To summarise, a patch to the documentation that provides an example service unit file has been submitted and committed, and it would be great if the unit file in the Arch package could also be updated (as this appears to be a distro's responsibility and is not provided out of the uwsgi box).