You could use software serial for the plotter.
I think that would need to connect to a TTL-USB cable to connect it to the PC ?
@purbluish, another option is to write your own PC program that takes a single stream of data from the Arduino and uses it to produce a graph and text output
I have never used the Serial Plotter (I am still at Arduino 1.5.6) so I don't know what it can or can't do. If you want to display a graph and the numbers that form the graph you may be interested in my EzScrn demo.