Postgresql 10 - Parallel Settings

There are 4 settings to enable parallel and optimizations, but documentation / a> in PostgreSQL does not say anything about values or calculations. My questions are:

  

1- How to calculate the values of max_parallel_workers ,    max_parallel_workers_per_gather and max_worker_processes ?

     

2- The work_mem can be calculated on the basis of connections and memory (RAM),   but does work_mem need to change anything if I enable parallel?

My guess is: if the machine has 8 cores, the max_parallel_workers would be 8 and the worker and gather process values would be 32 (8 * 4), the number 4 that I took from the original configuration which is 4 gathers per 1 parallel work.