5d mark3 , 70d, d5200, gh3, g6 for wedding videographer

[GEORGE]

Hi, This is my first post ever. Been doing quite a bit of research on this topic. I guess I'm what they called an enthusiast. My friends been doing lots of wedding and baptism videography with the 5d mark 3 .Loves the low ligh capabilty. He's looking to start his own co with a tight budget . He realy  wants 1080 60p.but also needs great low light.  Can the 70d ,d 5200,Gh3, G6 with fast glass be able to handle a wedding reception with insane lighting. One more ? 70d,gh3,g6. which one would be more reliable for focusing if left in background all by itself as a b camera... thanks hope to get some advice.  Can I also get some advice on some lenses. I have some on a list,  but I'm not sure whos been honest or paid to be honest out their in netland. .Realy love This whole eoshd forum its a heaven  sent to a newbie... .  My guess for cheapest is D5200 for low light or 70D with   ,and G6  with  for focus peaking and 60p. but not sure if its good enough to handle a wedding .. PLEASE HELP SUPPER CONFUSED WITH SO MUCH INFO OVERLOAD ON RESEACH.. .