So I'm considering getting a leopard gecko, so obviously I'm researching the proper leopard gecko care. But it seems like EVERY website says something different! I've read that you need a heat lamp to regulate the hours of lighting to mimic the hours they would get in the wild. I've also read that they can do well with just an under tank heater, and I've heard they need both. So... Which one is right?

also, the leopard gecko I'd be getting would be a 2-4 month old giant. So it wouldn't be a tiny hatchling or anything. So would it be ok to house it in a 20L if i put lots of hides and plants and such?

thanks!