I'm fairly new to the software so I would like to know how to get single chords to work without playing back in a predetermined fashion that is to say there always seems to be a rhythm behind the chords I would prefer to set my own rhythms like 16th notes or 8th notes,
You can change the chord playback sound by going to "Mix" and changing harmony and bass to "Piano" and "Piano Bass" respectively. By default harmony is "Piano 1/4s" and bass is "Piano Bass Dotted".
No, you can't change how they're played. However, you can simply subdivide the chord into whatever rhythm you want. You're not limited to half- or full-measure chords.