Nero's the best choice and plays nice with far more systems than any Roxio stuff. And if your burner came with Nero you got the full program. The EZCDCreator versions that are supplied with burners are stripped down versions.
The gap thing is confusing (as are quite a few things in Nero though.)
Just remember, the pause length you see listed after each track refers to the pause that precedes that track, and the first one (2 seconds) has to be there (although it can be made longer if you want, just not shorter).
To make a seamless disk you would change all (except the first) to 0 seconds.