alternative c++ library and eqivalent snippets in ros2

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I am trying to migrate my code from ROS to ROS2. Basically, it is a plugin (in c++) for the actor to follow a path. I am relatively a beginner in ROS2 and have some issues like

1. Is it wise to replace boost::thread with std::thread to implement a custom callback queue?

   private: ros::CallbackQueue queue_;

2. How to implement a NodeHandle or something like this (given below) in ros2?

   private: ros::NodeHandle * ros_node_;

3. What is the equivalent of the following code snippet in ros2?

   private: ros::CallbackQueue queue_;

I have referred to a couple of docs available online for migrating the code from ROS to ROS but nothing was useful. Can anyone suggest a solution?