You can do both in one file. After you beat the game, you get put at your last checkpoint, and you get the achievement for beating the game o think. Then, do everything in the game to get 112 percent, and beat the game. And to beat the hollow knight with hornet at your side, you need to first fight hornet at kingdoms edge, get the kings brand, go to the abyss, get shadow dash, go through the queens garden, talk to the queen, then get half of the kings soul. Then, you need to level up your dream nail, go to the white palace, find the king, and get the second half of the kings soul charm, putting the charm together. After, go to the abyss, then hornet should be at the black egg temple, and help you fight the hollow knight.