In DS 4.7 Point Lights do have falloff. So if they aren't very bright and they are a distance away, they won't contribute much light to the focus of your scene. 

As Bejaymac stated,  most people, myself included, do find the easiest way to place spot and distant lights is with the Perspective Camera. If I need to move them after placement, I look through the light to place it. 

Also included in DAZ Studio's base content are several additional lights. Uber Environment 2 allows you to set up Ambient Occlusion or  Global Illumination. There are also Shader lights for area lights and spot lights with fall off. If you decide that 3Delight is going to be your primary render engine then I definitely recommend Age of Armor's various advanced lights. 

One other thing, once you have your scene set up, turn off the camera's headlamp. It is only there to prevent black renders when a new user hasn't learned that lights should be in your scene. :) The easiest way to turn off the headlamp is to add a light to the scene. (If you are lighting with shader lights, then you can add a light and make it invisible, neither the invisible light nor the headlamp will give off any light with that combination. 

If you check the change log, DAZ Studio Iradium has a few light enhancements, both for Iray and 3Delight (not yet in the public Beta).

3Delight is pretty quick, compared to other render engines. Comparing it to Iray for speed depends on several factors. Your hardware, lighting and what you are rendering being the biggest. Remember, to get equivalent lighting between 3Delight and Iray requires, at a minimum, Uber Environment 2 added to your 3Delight scene.