I want to ask about Save config

> Is Save config not to lose settings even if the power is turned off?

Yes, in more details: The currently loaded running-config will be stored to the flash memory / NVRAM as the startup-config to be loaded at the next restart or after power loss.

> As long as you do not use SaveConfig, for example, if you change the VLAN settings, the settings will not be reflected?

On Netgear all changes done via CLI become active right after doing the config change. There are other vendors who use another paradigma where you change your config and nothing changes in real-life until you apply or commit the changes.

However if you mess up the config and you haven't saved the configuration, you can reload/reboot the switch and answer the question about saving the config with 'no' and the switch will forget all your trials/errors and reboot reload your (hopefully) working startup-config.

> Does the power supply restart with SaveConfig?
The power supply doesn't have much of a config, however a reboot or power cut will result in the switch booting the OS and then loading and applying what is in the startup-config