In the case they're successful, Galu gets trapped in Hell and, unless he gathers the intelligence to remember to just copy what Gotenks did or use SS4 to escape with Shunkan Ido, he's stuck there without Piccolo. That said, Super #17 kills all the Dragon Team until #18 shows up, at which point things go one of several:
1. Super #17 still kills Mu, but allows himself to be killed by exposing his weakness and having #18 destroy him with a Kienzan. The Dragon Balls are gathered to revive everyone and get Goku out of Hell, but the Evil Dragons break out. Because the GT cast either lacked the foresight or were too wary to use the Namekian Dragon Balls, they'd be lucky to even take down one dragon.
2. Same as the previous scenario, but Kibitoshin takes the risk of using the Namekian DBs to revive all those Super #17 killed and to get Goku out of Hell. The arc then goes exactly as it did in GT other than Piccolo helping out against Yi Xing Long and possibly still being alive by the 100 year timeskip, perhaps mentoring Goku Jr.
3. Super #17 kills Mu and #18, then goes about destroying all in sight. The Evil Dragons don't appear and Super #17 eventually destroys the Earth when he's bored of it, before moving onto space.
4. Similar to #3, but with Piccolo surviving and taking the risk of using the Ultimate Dragon Balls to erase Super #17. Assuming they live up to their hype and are able to do this rather than being resigned to the typical DB rules, the Dragon team have both the ticking clock of Earth's destruction and the Evil Dragons to worry about. Kibitoshin uses the DBs just as in scenario 2 and, assuming Goku has to leave immediately after Yi Xing Long's defeat, the remaining fighters explore space to gather the Ultimate DBs again afterwards and save Earth.
5. Super #17 defeats the Dragon Team, but listens to Mu, who then plans on using the Dragon Balls to become immortal or something. The Evil Dragons are released and Mu has Super #17 fight them. With how much weaker he'd be without SS4 Goku's Ki and how few of the Evil Dragons like to spam Ki blasts though, he'd be lucky to get past Wu Xing Long.