best setting is "game default" (or Disc default, I always forget the correct name), which is used to automatically set the console to the same region than the game you are playing.
If your Wii is in 480p NTSC and you launch a PAL game, the loader will set the console to PAL 480p
if your Wii is in 480i PAL and you launch a NTSC game, the loader will set the console to NTSC 480i
etc.
It uses the correct region while keeping the progressive/interlaced setting.
The patches are a little more harder to explain.
- VIDTV : I don't know what it does, sorry. It was there from the start, and I never had to use it.
- Sneek video patch : it's a method to patch video mode for imported games used by Sneek. I think only one game required it, I don't remember which one. So we added it to the loader just to let users select it.
- dol Video patch :
This one patch the list of video modes located in the main.dol of the game.
When you launch the game, the Wii check the compatible video modes found in the main.dol and choose the best one based on your current video mode.
If you set video mode to "force 480p" and launch the game, the wii is set to 480p, then the game launches and the console check the compatible video modes from the game. If it finds 480p then the console stays in 480p.
If the game doesn't have 480p in its list, the console goes back to one of the best match from the list (480i, 576i etc.)
"Dol Video patch" setting is a way to edit the content of main.dol to insert/replace your own video modes in the list.
If the game doesn't have 480p (for example Mario Party 8, Moto GP8, Mad World, etc.), you can add that mode in the list. When you launch the game, the wii will see 480p in the compatible video modes and will stay in 480p.
More information on the possible settings here:
http://gbatemp.net/threads/usb-loader-gx.149922/page-868#post-4802650