The main combination which will break your game is a Fighter using archery style, with crossbow expert and sharpshooter. If you have someone in the party that can cast bless as well, then you're in trouble. The up side is this combination doesn't start to become problematic until level 8 (more so around 11).
Other than that, the game is reasonably well balanced, especially levels 1-5 when you're playing LMoP. It really comes down to the choices the players make tactically rather than their build, although be wary of the poorly written stealth rules combined with cunning action, you may find your Rogue player getting advantage on every attack.
Other than that, the game is reasonably well balanced, especially levels 1-5 when you're playing LMoP. It really comes down to the choices the players make tactically rather than their build, although be wary of the poorly written stealth rules combined with cunning action, you may find your Rogue player getting advantage on every attack.