Right, I just blinded myself but I am sure that you will have a ground wire also as I do have on my cooltube. The easiest way to determine what the ground is, is to look on the cooltube side of things. Look at the wires that enter the tube and see what colours they are. Mines is a yellow wire for ground, the other 2 I do not have a clue as I was almost blinded by trying to look haha
The ground wire is the single one that is attached to the metal part of the cooltube. The other 2 wires go to the lamp holder inside the cooltube. They should have different colours for safety reasons, also making things easier to figure out.
You should be fine using them twist on wiring connectors, I have never used them but have seen them and they seem sufficient as long as you use the correct size and leave no bare wire showing which could cause fire or electric shock.
And about the digi ballasts, yeah any wire can emit RF. You know a simple length of wire can be used as an antenna that is capable of transmitting signals right around the world.
For wire to not emit RF it must also be shielded. I believe my ballast is RF shielded (Lumatek) but the cooltube wire is NOT. However the problems that arise that could get you busted is all related to cable internet, we do not have cable in my area so that is a bit of a relief. I have tested my setup with a regular AM radio to check if there is any noise on what would normally be a clear radio station. There is very little interference coming from my setup so all is good.