job queue used in app server

Hi, i was wondering if the job queue created in P986130 would always run in single-threaded mode or multiple threaded by default?  In what circumstances, we need to use multiple threaded mode....?

Say the queue created in favor of multiple threaded , so, it would use single or multiple threaded ? how about the JDE ube process , would it be single threaded mostly ?

is that good practice to assign specific UBE process to certain job queue ?

pls advice...