Different django rest approach for urls.py, INSTALLED_APPS, apps.py

reading few similar topics in stackoverflow and https://docs.djangoproject.com/en/3.2/ref/applications/#configuring-applications Im still facing issue understanding proper way of handling urls. I'm following two REST API tutorials in which they differ from each other about urls.py's, settings.py, apps.py files.

Having structure like this:

├───my_project
│   └───api
│       ├───apps.py
|       └───urls.py
│   └───my_project
|       ├───urls.py
|       └───settings.py
|   └───manage.py

Tutorial #1

my_project\api\apps.py

    from django.apps import AppConfig
    
    
    class ApiConfig(AppConfig):
        default_auto_field = "django.db.models.BigAutoField"
        name = "api"                     ########### DIFF
    

my_project\api\urls.py

    from django.urls import include, path
    from rest_framework import routers
    from . import views
    
    router = routers.DefaultRouter()
    router.register(prefix="symbols", viewset=views.SymbolsViewSet)
    
    urlpatterns = [                      ########### DIFF
        path("", include(router.urls)),  ########### DIFF
    ]                                    ########### DIFF

my_project\my_project\urls.py

    from django.contrib import admin
    from django.urls import path, include
    
    
    urlpatterns = [
        path("admin/", admin.site.urls),
        path("api/", include("api.urls")),   ########### DIFF
    ]

my_project\my_project\settings.py

    INSTALLED_APPS = [
        "django.contrib.admin",
        "django.contrib.auth",
        "django.contrib.contenttypes",
        "django.contrib.sessions",
        "django.contrib.messages",
        "django.contrib.staticfiles",
        "rest_framework",
        "api",                               ########### DIFF
    
    ]

Tutorial #2

my_project\api\apps.py

    from django.apps import AppConfig
    
    
    class ApiConfig(AppConfig):
        default_auto_field = "django.db.models.BigAutoField"
        name = "my_project.my_project.api"     ########### DIFF

my_project\api\urls.py

    from rest_framework import routers
    from . import views
    
    router = routers.DefaultRouter()
    router.register(prefix="symbols", viewset=views.SymbolsViewSet)
    ########### DIFF Lack of 3 lines

my_project\my_project\urls.py

    from django.contrib import admin
    from django.urls import path, include
    
    from my_project.my_project.api.urls import router
    
    urlpatterns = [
        path("admin/", admin.site.urls),
        path("api/", include(router.urls)),     ########### DIFF
    ]

my_project\my_project\settings.py

    INSTALLED_APPS = [
        "django.contrib.admin",
        "django.contrib.auth",
        "django.contrib.contenttypes",
        "django.contrib.sessions",
        "django.contrib.messages",
        "django.contrib.staticfiles",
        "rest_framework",
        "my_project.my_project.api",
    
    ]

I have put

########### DIFF where files are different and bolded text.

So the main interesting difference is in the file my_project\my_project\urls.py

1. Why there is sometimes api and sometimes full path my_project.my_project.api?
2. Should I use full path always or short one?
3. Why in first tutorial we have used urlpatterns in my_project\api\urls.py and not in tutorial #2?
4. Which of this tutorials is closer to best practices?
5. Why one time we have

path("api/", include("api.urls")),

or

path("api/", include(router.urls)),

To get same return from include for the first one I need:

include("my_project.my_project.api.urls")[0].router.urls[0]

for the second one

router.urls[0]

so why "api.urls" is working?

Hope that some questions are clear, thank you for any tips & help! Have a good day!