Glad you're feeling reassured. Puppy play can sound like a murder is taking place, so realize that's perfectly normal. Loose, wiggly, romping, leaping, boxing, grunts, growls, and barks, are what you want. If Puppy A is being a bully, Puppy B will crouch, try to hide, and cry. If Puppy B is being chased, rolled, battered, then gets up and runs again with a tail up and body loose, it's play. Some puppies enjoy being chased for fun.
My puppies Francis and Noelle played a game called, "Francis has a thing." Francis would get an item: a stick, a scrap of a toy, and then tease Noelle with her new thing. Then she would take off running. Noelle would chase and try to get the item. Francis dodged her, rolled, and ran away with her thing again. It was loud, and ridiculous, and obviously a game. Noelle never actually tried to get the thing Francis had. And if Francis dropped it, Noelle would wait for Francis to grab the thing and start the game over. They still play Francis has a thing sometimes. Delights me every time I see it.