CpuMenuBar is a light-weight application that resides in the macOS menubar. It gives a visual display of the current CPU usage as a bar graph. Users of the Task Manager on Windows will be familiar with this interface.
Clicking on the icon opens a menu which displays several items:
-CPU usage details over the past minute or so, displayed as a line graph
-Current RAM usage, broken down by type
-System information, particularly info which isn't convenient to find via the system menu
Plus, CpuMenuBar is very low impact - it uses just a fraction of the processor time and has a far lower energy impact than having the full-fledged Activity Monitor app open. For convenience, you can launch Activity Monitor from the CpuMenuBar menu in one click, should you need more detailed information.
Options include the ability to change the display update speed, the icon display details, and the colors which are used to draw the graphs.