Best practices for optimized data transmission

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Hi, I would like to ask you which are the best practices for creating optimized ROS projects.

I'm using ROS2 bouncy, but I think the issues applies to ROS1 as well. I have some nodes which publish sensor data and many other nodes which require only the data coming from specific sensors. There are different threads, some nodes are on the same thread. All sensors data are published more or less at the same frequency.

One node provides data A and B. Then other nodes want to access this data through subscriptions or client requests. Some nodes require only A, some nodes only B and some nodes both data.

    void f1()
    {
        auto dataA = ... coming from subscription/client to dataA ...
        cout << dataA <<endl;
    }

    void f2()
    {
        auto dataB = ... coming from subscription/client to dataB ...
        cout << dataB <<endl;
    }

    void f3()
    {
        auto dataA = ... coming from subscription/client to dataA ...
        auto dataB = ... coming from subscription/client to dataB ...
        cout << dataA<< " " << dataB <<endl;
    }

How should this data be provided by the first node?

1. create two separate publishers/services (one for A and one for B)
2. create a message which contains both A and B, to provide it through a unique publisher/service (even if some recipients will only use part of the message)

How should the functions use the subscription/client API ? Note that they are all non method functions (i.e. they are not part of a class)

1. each function has its own node and subscribers/clients (all global variables) initialized at the first function call
2. there is only one node common to all functions, each function has its own subscribers/clients
3. there is only one node with a subscriber/client for each available data

A process requires once in a while a continuous stream of sensors data for a relatively short amount of time.

    void f_loop()
    {
        while(1){

             sleep(5 minutes);
             start_time = time;
             while (time <= start_time + 15 seconds){

                   auto response1 = ... client 1 request ...
                   cout << response1->data <<endl;
      } } }

What's the best ways for accessing this data?

1. creating a subscriber at startup and spinning only when the data is required.
2. creating a subscriber every time data are required and then letting it go out of scope to unsubscribe
3. use a service

Thank you a lot