When’s the best time to light? Erev Yom Tov or Yom Tov by night?
There are differant customs, and if you have a family minhag do that.
There is a few benifits to lighting erev yom tov, that you have tosefes yom tov, because she is mekabel yom tov when she lights. Secondly, she doesn’t have the issue of that the candle you are lightnig with, will drip, which may be an issue of mechabeh, because when it tilts it loses wax, causing it to extinguish quicker. (This can be avoided by lighting with a match). Just one thing to bear in mind, that if you will light when it is already yom tov, you have to take th fire from somewhere else, and you can not put put the match when you are finished.
On the second night of yom tov everyone lights after it is already night.
There are differant customs regarding the order of lighting on erev yom tov. Some light the candles and then say the bracha, as they do on shabbos. Others make the bracha before lighting, as we usually do when doing a mitzva, “over l’asiason” (before doing it). When we read the megilah of shake lulav, we say the bracha before doing the mitzvah. (On erev shabbos we don’t do this because she is mekabel shabbos when she says the bracha. Therefore if she will say the bracha before lighting it is already shabbos and she can not light the candles! Therefore she makes the bracha after lighting the candles. On yom tov however she may light candels after it is yom tov already so she may say the bracha before lighting.) If you are going to do like this custom, she may strike the match before lighting, then she makes the bracha, (is mekabel yom tov when she makes the bracha) and then lights. Since she was already mekabel yom tov, she may not put out the match, but she should place it down so it will go out by itself.
Have a good Yom Tov
Introduction to the Tur by the son of the Prisha, Mateh Eprayim 625-33, Shmiras Shabos Kehilchoso 44-2, 7, Shulchan Aruch Horav 263-8, M:B 263-26.