[Mark McLeod]

You don't need the radio if you use USB for Run as startup . It's not in the path and doesn't give out the IP addresses used by the roboRIO or PC over USB.

If you are using Ethernet, then through the radio is easiest. The radio is assigning compatible IP addresses to both the roboRIO and PC.
The radio is necessary for downloading code over wireless, of course.

You can use Ethernet without the radio there to serve IP addresses, either connecting through a bridge or directly between the roboRIO and PC. In fact that's essentially how it will work in the pits at competition. At competition the robot's OpenMesh radio will be setup as a bridge and won't be serving DHCP addresses, which is the playing field AP's job. So, in the pits the PC and roboRIO will both resort to compatible default IP addresses in the 169. range.
The trick is that the roboRIO will take it's default address as soon as it boots and doesn't find a DHCP server. The PC needs to timeout it's IP assignment if it's been connected to a DHCP server in the recent past. Some PC's are quick to reassign when the DHCP server disappears, while others are slower.
Just be aware that it's going to be smoother if you avoid unnecessarily switching back and forth between connecting to the radio and connecting directly to the roboRIO via Ethernet.