Being closer to the light will make it grow faster, but if its really low light it may not be much of a difference. It grows like mad under higher lighting with co2/ferts, I had to trim mine constantly when it kept it under higher conditions, but now that its in a low-medium setting I rarely have to trim it back at all, maybe once a month.
You can cut it wherever you want to, the cuttings will become their own plants, so to speak.