Determining Whether Query Load is Too High for PostgreSQL Server
This is not a horrible load for modern server hardware.

On a write heavy DB its going to be dependent on the Hard-disk layer, triggers, functions, indexes and constraints that have to be processed/checked. 

An easy way to get to the information you want is to install pgAdmin,  and use the dashboard to see what is going on. Number of connections, transactions per second, tuples in and out  

From there need to study system load using,  some kind of System Monitor,  i like glances,  this will get the information on the CPU , Network and HD loads,

If there is significant wait times on the CPU or HD,  can adjust the log settings in postgresql.conf to record which queries take longer than X time