At what piont do you see issues? I'm on the free tier and only have about 3GB of files and have never noticed any CPU usages issues with Dropbox on my Mac
I checked right now and the Dropbox process on my machine has consumed a total of 39 minutes CPU time. That's 39 minutes of full-scale CPU usage. Even their "web helper" process (whatever that is) consumed two minutes and 41 seconds.
This discussion is about performance of the macOS client. Saying that clients for other OS work well doesn't really contribute to it.