Zarbon told Appule if he found any village, he is to inform him since he can't handle more than one. The Namekian Warriors were 3,000. Piccolo at best is 3,500 based off the Daizenshuu.
Tough fight, but Piccolo wins since he is more smarter in combat and this is just Base Appule, not Lord Appule.
Appule beat Vegeta to an inch of his life (Budokai Tenkaichi 3 profile) and has always been the fourth strongest henchmen Freeza has with him. He stopped training and decreased to the point where a Namek villager can handle him.
Piccolo ain't touching Appule Pre-Namek no matter what. Post? Yeah, it's most likely Piccolo who'll take the win.
Just think about this: if Appule disobeyed Freeza's orders and went to Earth, flew to Karin's tower and threw him off the tower, Appule would be the new Co-Guardian of Earth. We need a special Appule what-if, whether it's a manga chapter, anime movie, or a video game story.