This is with the Sola 500's so if you can get decent results with these then any of the range will do ok. At night I dont think you'd be needing to use 1200 lumens but daytime is when you need all the lumens you can realistically afford. Seeing how bright these lights look and everyone that did this dive was impressed how well it lit everything Id love to see what a pair of 4000's would do lol.
For close objects which is where the GoPro works best anyway the 500's do a pretty good job from what Ive seen so far. Close objects at night even 2x Sola 500's are too bright at times so the more lumens would let you shoot things further away but you will be turning them down to shoot anything close.
The best thing about these lights though is how wide and even the beam is with very soft edges, I assume that all Sola lights in Flood mode would perform the same. For a Gopro you do really need a very wide beam spread as it does have a very wide angled lens.