Re: Best theme to start with?
Standard theme is stock and it is updated together with the core. You will not see separate update download.
Crisp White is separate module so it has to be updated when there is core changes which affect anything the theme touches.
You can uninstall Crisp White, you cannot uninstall Standard. There is always one stock theme which is part of XC core - in this case Standard.
You can develop based on either one or have your own completely done from scratch.