I have some tips I used to beat 4/20 but i know for certain that they won't be 100% useful cuz due to the AI lv difference especially bonnie and Chica and probably harder on n6
Bonnie/Chica- unless its while your opening or closing the camera you will hear walk up to the door so you as long as you listening carefully you never need to check the cameras for them, (this is where the lv 20 difference comes in probably in a harder way) after you can hear them walk you can wait like 3 seconds before closing the door then just check for them to leave which happened almost instantly if done right on 4/20 but will probably take longer for you. P.S. If you don't know to tell if bonnie left there is a gas mask like sketch in the bottom right corner of the window which if Bonnies not there it will glow cyan'ish when the lights on
Foxie- She will/is probably the main problem, every time she attacks in the current patch (0.0.7) does more power drain each time she attacks where at the 4th attack she does around 12% drain so to try limiting this, check her room (which is the only camera you need to look at till 5am) on and off example 3secs on 6secs off (what i was doing) to get her attacks to happen at least slightly later giving overall more time. you don't need to check the camera to make her run if you have a good reaction time after she leaves her main room it will take longer for her to attack if you don't check that other camera and you can hear when she is running directly to the door saving you a little more time.
Freddy- Freddy is the easies one to beat, even if she gets to her last room (after 5 laughs/giggles) before 5am she wont attack till after 5am at a random time. there is currently a glitch or intended mechanic (idk which) where if you put your camera on that last room it stops her from attacking. you don't have to be actively in the camera for this to work.
you will probably lose all power before the night ends putting you in the hands of Freddy and if you got lucky during the day you got far enough into the last hour to make it i know personally i beat both N6 and 4/20 without power.
Sorry if this was hard to read I'm not great at writing and just threw all the knowledge I had to try and help.