These are environment variables which you can specify when starting guacozy-server:

DEBUG : Django DEBUG mode

DJANGO_ALLOWED_HOSTS: Let's you specify allowed hosts to prevent host header attacks (Read more)

DJANGO_SECRET_KEY : random string used for hashing (50 chars)

FIELD_ENCRYPTION_KEY - encryption key which will be used to encrypt passwords in database Read more

DJANGO_TIME_ZONE : timezone (e.g. Europe/Vilnius)

DJANGO_DB_URL : DB URL - read at django-environ documentation

SUPERUSER_NAME,SUPERUSER_EMAIL,SUPERUSER_PASSWORD : use these if you want default admin to have specified values

If you don't specify SUPERUSER_ values, user admin with password admin and email admin@example.com will be created.
You can always change admin's email/password later, however if you ever delete "admin" user it will be recreated on next startup.
So if you are unhappy with admin username, specify just it (you can specify name/email and skip password)