First yes it will be noticeable. Mouse moving is very sensitive.
Let’s start with MVC. Its a design pattern often used in games: model-view-controller
The model is your entitydata only relevant data for the game state. The view handles how things a drawn. And the controller handles the logic. Think of a player entity. It has a position and maybe a definition for its physics shape (a capsule). The logic moves it (If key up is pressed change the position component). Then you have a spatial. (I use the term spatial and not model to not confuse you with the design pattern model which is only data). But who cares about the spatial? Only the view. It uses the position to put the spatial at the right place in the scenegraph. No need to set the spatial on the server.
Now let’s come to the view direction. Of course you want to turn the character if you move the mouse. But who cares about this? The model doesn’t because a capsule looks always the same. You can’t turn it. Only the spatial (or camera direction) should be turned.
Hey it’s a shooter and I want to shoot at a certain direction! The logic which processes the shoot (raycast, lower health component, raise score component,…) should run on the server. No problem in this case you separate the view direction from the view. Keep updating the camera as described above but additionally call setViewDirectionComponentOnServer() to update the entity data. This call could be less frequent and doesn’t need to be instant because the view direction component is never used by the client. It is only used by the server( which handles the game logic) to process the shoot logic. It is ok to have lag between the input and the shoot logic because in most cases it doesn’t matter if you get a point 200ms later. But it does matter if it needs 200ms to turn your head.
Fast paced network games are difficult because you have to think about the lag. There are multiple techniques to enhance the feeling of the game but most of them have their downside. You will have a hard time getting them right but be comforted even big commercial games have their issues with multiplayer.
Edit: I just saw that you use a better character control
I don’t know how it is connected to your entity system and I’m not that sure how it uses the view direction but I can explain how I do the movement.
I calculate a movement vector based on the view direction and the pressed keys on the client and send this vector to the server. This vector could be used to move your character control. And then the resulting position could be set as component and send to the client via ZayES networking. I think pspeed has some special components for positions. They should be used in the examples. As you see I wouldn’t use the view direction on the server for movement.
That’s the reason why I would update the camera without asking the server (see point 1). And the logic is allowed to be delayed.