lowering temp will have adverse effects.
Stringing with pla - should not happen.
You need to try Cura and have a look at the retraction settings.

Think my pla settings are 2mm and 60mm/s retraction.
Don't get any stringing in standard pla.
I also keep my movement speed the same as my print speed. The sudden changes in speed will also result in stringing and little spikes of filament.
Slower movement and faster retraction will reduce stringing.
Higher printing temps will also help. My standard pla print temp is 210.

As far as start and end code goes - try it and see - can't hurt the printer :-)