Single player help

I want to play alone, but I saw suggestions that if you play single player to make sure you adjust the settings. If I adjust the settings, do I miss out on achievements and such? I'm not sure how this game works, but I like to play games as they are originally attended (no cheats/mods "easy route") Yes, I know I miss out on things playing single player. Any suggestions on single-player settings? I'm very intrigued by the game, but I hate I miss out if I choose the single-player route 😩