GO Contact Sync Mod uses the Google OAUTH protocol for login. It is not a "less secure app" so that setting under Google need not be activated.
In the People App, in its settings, there are settings for each individual account you create. I don't know that the default sync interval is, but you can set the sync interval to your liking and it should be automatic. I've never manually synced in People, including for my testing contact to ensure that syncing was occurring.
Brian - Windows 10 Pro, 64-Bit, Version 20H2, Build 19042
There are many who labor under the gross misapprehension that the Constitution is a cage and a laundry-list rather than a framework upon which great things have been and still will be built. Many things that are entirely Constitutional are not "in the Constitution," but are allowed under it.