For a deep tank like this , you'd need 20 watt lights , min .
I don't have carpet type plants , so I don't know how they would do with the lights in a tank that deep ,
but in a shallower tank I think they'd probably work fine even for those plants.
In this tank , when the fish swim a couple inches from the bottom , you can definitely see their shadows - So that tells me it's pretty bright
The lights I have are "flood" lights with a 120º spread - You can also get them as spot lights , which will penetrate deeper , but if the water is even a little cloudy , you can really see "cones" of light with those .
If you buy them , make sure you get the "day-white" ones - those are about 6500K , and look pretty good - The "warm white" ones will look really yellow in an aquarium .