GG4 and Wedding Cake have been around for quite some time and should have pretty stable genetics as long as they came from the same source.But yeah, if they were just in a bag then you never really know what you have. A few years ago I grew some feminized White Widow and Original Skunk from Canuk and both were awesome. About 8 of 10 seeds germinated within 48 hrs so they were likely pretty fresh stock.
There are a lot of good grow lights out there now, it can be hard to make a choice for sure. If you're working in a grow tent or room that is 4x4 or larger then my suggestion is to get a light setup that will cover your entire canopy as evenly as possible. This gives you even coverage and penetration from the center out to each side. If you train your canopy to be as even as possible having even light coverage will help keep your colas the same size as well. I prefer the arrangements that are composed of a series of light bars on a frame that can be spread out evenly over a 4x4 space. I also like the setups that have dimmers so you can adjust the output to find the best combination of strength and penetration for specific growth stages.
Four a 4x4 or 4x6 grow space I'd probably go with a light that has a 4x4 footprint directly beneath the light, for a 4x8' area I'd use two lights with a 4x4 footprint.
How many watts a light has isn't really a good way to measure how much light it puts out at any specific distance above the canopy. Of course the more watts means it uses more electric power so its likely going to put out more light than one that draws less watts, but not necessarily. The best way to tell how a light is going to perform is to get a PPFD map from the manufacturer. This will show you how even the coverage is over a specific sized canopy and It should also tell you how much light reaches the canopy at any given height.
For instance the lights I use now (SPYDRxPlus) have a 4x4 footprint of evenly distributed light intensity. At full power they produce 911 PPFD at 6". 745 PPFD at 12", 594 PPFD at 18".
Young cannabis plants grow well at about 400 PPFD, vegetative plants between 400-800 PPFD and flowering plants between 800-1400 PPFD.
All plants can use only so much light. With cannabis anything over 1400 PPFD is unlikely to aide growth and your plants will likely need CO2 supplementation if they are going to make use of more than 1000-1200 PPFD.
PPFD is measured in umol/m2/sec. All reliable manufactures will gladly provide this information_ if they won't then I'd be suspicious. A PPFD map will show how much light intensity drops off as light spreads out from the center. Of course the higher the light is above the canopy the more even it will be over a larger area but the weaker it will be.
The best choice will be whatever light or combination of lights will produce 400-800 (or more) PPFD over your entire canopy, not just the central area beneath the light.
Hope that helps.
I can send you more information about PPFD if you wish, just let me know.
Cheers!