Plebes is a very popular slang word from Sinaloa, Mexico, a region known for this style of music. It's a colloquial term used to mean "dudes", "the guys", or a person's crew or entourage.
In the song, Peso Pluma sings, "Mis plebes en Suburban iban atrás" (My guys were in Suburbans behind me), referring to his crew following him. Learning a word like plebes is a great way to understand the specific culture and flavor of Regional Mexican music, as it's not something you'd typically find in a textbook!
Peso Pluma tells a story from the perspective of a powerful young man in Culiacán, Mexico. The song is basically a blow-by-blow account of a failed attempt by the authorities to capture him. He says, "Quisieron apresar / Al joven que comanda la capital" (They wanted to arrest / The young man who commands the capital), but it didn't work out for them: "No se lo pudieron llevar" (They couldn't take him away).
The whole song is full of these kinds of boasts and details about a life of crime. The narrator talks about his crew in camouflage, his armored truck with a roaring supercharger, and his personal style, which mixes luxury fashion with military hardware: "Piernera las botitas Dior y una scar" (A thigh holster, Dior boots, and a Scar rifle). He makes it clear he's loyal to his side, declaring "La bandera de aquí sigue siendo Guzmán" (The flag here is still Guzmán), a direct reference to the Sinaloa Cartel. It's a song about power, escaping the law, and controlling a city through force.