I think Hybrid mode refers to an ability in the programming of the smart strings, whereby you have the best of both worlds: string mode (i.e. red for all, green for all and blue for all ... all nodes on the string) and pixel mode (rgb for each pixel). So if you had a 128 pixel S String, in hybrid mode 1-3 would be the string mode operation of R,G,B (for all pixels) so 1=red for all, 2=green for all, 3=blue for all ... and 4-131 would be the RGB for each of the 128 pixels so pixel 1 would be 4,5,6 (4=r,5=g,b=6) and pixel 2 would be 7,8,9 (7=r,8=g,9=b), and so on.
Again, talking about programming the smart strings, then you would see in LSP as 131 channels x3, so 393 total.
That my understanding of Hybrid mode (coudl be a tad off) ... but I about died of excitement when I watched RJ' video on it last night ... and he was showing both modes and the prorgamming, etc.