Is there a system where plane/heli auto adjusts prop pitch/mixture?
There sure is but it is generally independent of what is traditionally considered a "glass cockpit" and is often wrapped up under the FADEC system. One of the earlier production designs for this found its way into the Mooney M20PFM which was a Porsche Powered Mooney that had an electronically inject 3.2L Porsche car motor in it. Most importantly it had "single lever operation" where the throttle, prop, and mixture were all wrapped into one lever. For a variety of reasons the plane was ultimately a failure and I do not belive any are still flying with the Porsche motor.

As Ron mentions in the comments some of the Diamond's like the DA42 are set up this way.  


  So I can only spend time adjusting throttle?


This is perhaps the more important part of the question. Perhaps one of the main reasons that planes are set up with the throttle, prop and mixture adjusts is to allow for fine control. Automatic control systems generally operate in the most "efficient" range but as a pilot you may wish to operate in other ranges, run lean of peak or cruise at a very slow but efficient burn. Your POH will give you all the relevant information to operate your plane in all sorts of ways.