Monitoring system vital signs by
conky and other similar applications is done with a combination of setting up event handlers and periodically polling various pieces of data.
Where the CPU time is really consumed is during the polling which is why when you pause
conky you see the drop in CPU usage.
There are two fundamental approaches to reducing the load on the CPU of an application polling. The first is to increase the polling period so that the application is not polling as often. The second is to reduce the number of things polled and the effort spent polling.
I suppose there is actually a third approach which is to reduce the load imposed by the User Interface. So a graphically intense User Interface with graphics and images can impose more load on the CPU and GPU than a plain and simple presentation of the information.
I suggest you experiment with
conky and check the CPU usage to see the effect of the change. The first thing would be to turn off the reporting of information you do not care about. Secondly would be to increase the polling period. Thirdly would be to go with a simple and plain theme.
See this article Expert's Guide to Configuring Conky as a starting point.
Here is a link to the
conky wiki which has a lot of information about the various settings. You will need to review what work your installation of
conky is doing and decide what things you are willing to do without.