That about sums it up. It's for you to sit and watch your fish do their thing. Some fish really enjoy having a few hours of moonlighting. Many of them are very active during that time (Otos, Loaches for ex). Others are said to be induced to spawn.I like the way they look at night.
I would keep the intensity low, and only run it for a couple of hours so your fishies still get a bit of a dark period.
It shouldn't affect the plants at all.