(Without reading all the way back through this thread,) I think joemike has omitted an important point, i.e. that "90%" CPU usage probably isn't a very high number, because most, possibly/probably all, Macs these days have more than one core - my 2016 MBP is a 6 core machine - and each of them can show up to 100% CPU usage for a possible, albeit unlikely, total of - really - 600%.
I frequently see numbers greater than 100% with absolutely no apparent hit on machine performance.
I think that offers some clarification of his last post.
