I have seen some calls for help in the comments and here I arrive after 100%ing the game.
There used to be a guide on a fan wiki- but that got taken down, so I will share the wisdom i've learned with the new version.
First and foremost the first thing you need to learn is three very important audio cues:
-left footsteps means Bonnie is at the door
-right footsteps means Chica is at the door
-Giggle means Freddy has advanced a stage (or retreated if at the final stage)
We should all know the basics of fnaf to know you shut the door on both Chica and Bonnie.
Where this game differs compared to Fnaf 1 is power and how Freddy works.
Freddy will progress from the stage to the toilets, to the lobby, to the skeleton room, to the broom closet to the kitchen. Whenever Freddy is in the kitchen shut the right door down. Once you hear another giggle that means Freddy has retreated to the broom closet and will then advance into the kitchen again next giggle- rinse and repeat.
It is important to note that ANY camera usage will prevent both Freddy and Foxy from advancing their stages. My preferred strategy and what I used to beat 4/20 mode is to just prevent Freddy from getting to the closet as soon as possible. Also note that its good to check in on Foxy, as even if you hog the Cameras, just being off them for 5 or so seconds can advance the stage if you're unlucky. Make sure if she leaves the cove that you shut the door and check the hall to see her run. If you don't then you might as well restart because 30% of your power will be gone. If you do about 3-5% will depart your systems. Also, make sure to wait for all the knocks to finish- I've made this mistake once.
Another important thing to keep in mind on the tougher nights is that you will require some rng. From my knowlege it is close to impossible to beat nights 6 and 7 (4/20) without losing power- it used to be that way before 1.0 and it's the same way now (in fact harder with the new Freddy). Furthermore Bonnie and Chica move rather randomly, sometimes attacking other times just running to random rooms in the facility while never bothering you. You can get screwed over by just having them decide to attack more than usual- taking more power and letting Freddy advance a stage. Your main goal is to get as far into 5 A.M as possible and pray.
Once you beat 4/20 mode, to get 100% completion just get jumpscared by each girl at least once. After that type in 1 9 8 7 in the character select on night 7 then beat the night. After that repeat with 6 9 6 9, though this causes a golden Freddy jumpscare and H scene. After that, you should have 100%.