Would you prefer a single app or multiple apps

I recently tried actix-web framework but I am confused about how to use actix-web properly.

Should I use multiple app (*example from actix-web doc)

let server = server::new(|| {
    vec![
        App::new()
            .prefix("/app1")
            .resource("/", |r| r.f(|r| HttpResponse::Ok())),
        App::new()
            .prefix("/app2")
            .resource("/", |r| r.f(|r| HttpResponse::Ok())),
        App::new().resource("/", |r| r.f(|r| HttpResponse::Ok())),
    ]
});

or single app

App::new().scope("/project", |proj_scope| {
    proj_scope
        .resource("", |r| {
            r.method(Method::GET).f(get_projects);
            r.method(Method::POST).f(create_project)
        })
        .resource("/{project_id}", |r| {
            r.method(Method::PUT).with(update_project);
            r.method(Method::DELETE).f(delete_project)
        })
        .nested("/{project_id}/task", |task_scope| {
            task_scope
                .resource("", |r| {
                    r.method(Method::GET).f(get_tasks);
                    r.method(Method::POST).f(create_task)
                })
                .resource("/{task_id}", |r| {
                    r.method(Method::PUT).with(update_task);
                    r.method(Method::DELETE).with(delete_task)
                })
        })
}).scope("/user" ?????)
    .scope(????)

It’s up to you, but most likely single app will be enough, so keep it simple. The only reason to have multiple app I can think of is if you want to have them to store different states (beside splitting them for better code organisation).

What are apps here (in Actix)? Can we compare them to Django apps or Flask’s blueprints?

How routing would be in first approach (multiple app)? This would be a “two-level” routing?