Vertical accuracy can be held very well anywhere from 0.5m to 4m.
As to the light, after reviewing flight test logs, I see that the flow algo reports best quality with full sunlight. However, it needs not always have 100% quality to perform well. I've tested in daylight shadow, just after sunset, and indoors during the day without artificial light and in each situation it was able to perform well. I've also tried it at night with some (poor) indoor lighting and could not get enough gradient to work well.
In the end you would need to analytically determine how much light is needed to work within given parameters. The camera sensor also has quite a few parameters that can be tweaked to control how it handles light levels.