"visible" -> Is this setting visible by default for this printer (can be overriden by user)
"active_if" -> We used that in old versions, but we no longer do it like this. Has been replaced by "enabled" property, that can now have functions instead of just booleans. Not all machines are updated (as we only update our own machines)
"always_visible" -> That setting doesn't exist.
Machine settings can (by default) not be changed by the user as they are machine specific (eg; changing them would imply that the machine is no longer the same). If you make modifications to your machine, this should result in a new .json file (with those parameters changed).