Advanced video settings?

I'm a new RasPlex user who is not a former XBMC or OpenELEC user, so I don't know how many of these settings are Rasplex specific vs XBMC.  In any case, since the Raspberry Pi is a known quantity for Rasplex, I figured there must be some preferred settings.  My TV is a modern Plasma capable of 24p, 30, 60i, 60p

Can anyone describe what these settings are for?  I have an idea what they do, but not necessarily under what circumstances you would want to enable them.

 

1) Adjust display refresh rate to match video

  Off vs Always vs Start/stop

 

2) Sync playback to display

  What benefit does it provide, and which method is the best? (video clock, audio clock, resample)

 

3) use FFMPEG AVIO for network transport

 

4) Remote control sends keyboard presses

  Seems to work fine with and without it.  What does that do?

 

5) Vertical blank sync