NeoGamma r7/8 will load 99% of backups.
NEVER updqate your Wii after modding if you like your homebrew and playing backups. It will kill all these functionalities. I've also heard that the 4.2 update could possibly brick your Wii [even un-modded ones]. But this is rare.
As far as the 3 channels part, that will not happen to your Wii. You will still have all the channels you normally would. They just deleted all the "unecessary channels" so it's easier for the user to see what channels they will mostly be using.