MongoDB - What Scales Better, An Array Property, A Nested Object Property or Putting That Data In A Separate Model?

Here's a data model for an application with a REST API that will hopefully scale to be quite large (if I'm lucky). I've read about difficulties that can arise with Arrays in MongoDB, so I'm hesitant to use them. Here are the specific requirements for the applications:

• The Arrays will contain objects
• The Array Objects will be modified frequently
• There will be a lot of queries performed on the objects in the arrays
• The Arrays will never exceed a maximum of 30 objects
• I would like the REST API to send out data with Array properties, given they are simpler to work with. Of course, how we save that in the database can be different...

Given these specific requirements, which of the below models should scale better using MongoDB?

An Array for Order.products

var OrderSchema = new Schema({
    customer_name: String,
    products: {
        type: Array, 
        default: []
    }
});

A Nested Object Order.products

// Converting the array items to nested objects before saving, and performing the reverse before sending them back to the User.  
// For example, Order.products = { one: {}, two: {}, three: {} }

var OrderSchema = new Schema({
    customer_name: String,
    products: {
         type: Schema.Types.Mixed,
         default: {}
    }
});

Or Putting Those Items In A Separate Data Model...

var OrderProductSchema = new Schema({
    order_id: { type: Schema.ObjectId },
    product_title: String,
    product_price: Number
});