Hello there!
So I’ve managed to make the camera rotate left, right, and back to the original position using multiple tweens. Sadly, a big problem with this is that, since it is a local script, it may cause lag on the client since the player will need to look left and right a lot during gameplay.
So, is there any way to reduce client-side lag from tweening, or should I make tweening happen on the server?
Any help is much appreciated 
Tweens don’t consume very much processing power, or create much lag, unless you have a bagillion of them. As long as you aren’t tweening every millisecond, you should be fine.
Plus, it’s better to have a bit of client lag, than lag on the server that affects everyone.
I address this problem as I am making a fnaf fan game and tweening will only be used for both cameras and doors.
But thank you so much for telling me this as this gives me some peace of mind! 
Plus, I can always add a bit of a cooldown between tweens so not many are played so often.