Hello,

I'm not sure I understood all your issues, so I'll try out some suggestions:

- The ALSA-related options are defined in the `(gnu services sound)` Guile module.
  Import the module to your config file and it should fix your issue.
  This is documented in the "(guix) Sound Services" section of the manual.

- NetworkManager: have you tried it?  Does it work?  You might not have the same
  issues with it on Guix than on Funtoo.  I suggest you give it a try first.
	Like you, I had a poor opinion of NetworkManager before I tried it on GuixSD.

- If you really want to turn off NetworkManager, I suggest you remove the
  service from your config.  For instance (untested):

  (services
     (remove (lambda (service)
               (eq? (service-kind service) network-manager-service-type))
             %desktop-services))

  With NetworkManager disabled, wpa_supplicant and dhclient should also be
  disabled.  Check the running processes.

  - If you want to run the wpa_supplicant Guix service, I don't know you can
  specify a custom config.  From the documentation and the source code in
  (gnu services networking), it does not seem to be customizable but I suppose
  that it reads /etc/wpa_supplicant anyways.

  - Otherwise, disable wpa_supplicant / dhclient services just like you did with
  NetworkManager if necessary.  Then you are free to run them manually with your
  custom script.

Hope that helps!

-- 
Pierre Neidhardt
https://ambrevar.xyz/