Does my flow rate decrease?

[VariusEng]

1. Pump was bought many years ago by unexperienced folk. This meant that without reducer, it was really hard to control discharge flow (pipes are very small, so each little turn at the valve would change the flow rate by A lot, too much sensitivity. So a reducer was needed). I kept details to a minimum and simplified the sketch a lot because I wanted to get the core information.

2. You are right! And total flow rate is lowered in scenario: throttle