Questions about MSFS24 career mode

So, in career mode when I'm flying missions, I've noticed that the blue flight pathing boxes and the magenta line on the compass in the top left corner don't exactly match up with the Garmin magenta lines. Is there a reason for that? Do I have to stay within the blue boxes to get the best score? I'd like to be able to take full advantage of the autopilot and to turn off the flight assists but I don't want my scores to tank lol. Also, I'm fairly competent at flying but I've never really learned airport rules. Is there somewhere I can learn about traffic patterns, how I'm supposed to enter and leave, stuff like that? Once again, I'd like to turn off the flight assists but don't wanna tank my score cuz I pissed off the ATC. Thanks I nadvance