🐛 Description

ProjectSettings.get_setting boils down to a Node.get call under the hood, so I'd say it's fine as it is. But if you want to be proactive about perf, feel free to introduce a variable with an underscore prefix that's initialized in _ready and use that.

According to the above, all invocations of ProjectSettings.get() call Node.get() which I assume is a property getter (via string!)
ProjectSettings.get_setting is invoked at least 5 times per tick in RollbackSynchronizer so as the quote says, all of these project settings which are read-only should be cached.

Example code below for reference of current project settings implementation

## How many ticks to store as history.
##
## The larger the history limit, the further we can roll back into the past, 
## thus the more latency we can manage.
##
## [i]read-only[/i], you can change this in the project settings
var history_limit: int:
	get:
		return ProjectSettings.get_setting("netfox/rollback/history_limit", 64)
	set(v):
		push_error("Trying to set read-only variable history_limit")

and from what I understand should be done (correct me if I'm wrong)

var _history_limit: int
## How many ticks to store as history.
##
## The larger the history limit, the further we can roll back into the past, 
## thus the more latency we can manage.
##
## [i]read-only[/i], you can change this in the project settings
var history_limit: int:
	get:
		return _history_limit
	set(v):
		push_error("Trying to set read-only variable history_limit")

...

func _ready():
      _history_limit = 64

So probably a function at _ready() is required to be added, which sets all starting values for the project setting variables.

Btw, I suggest first doing a search in godotengine if it plans to cache the project settings variables, so we don't implement it here and have it be needless by godot in the future.