Re: widget showing CPU and RAM usage
If that was part of the Windows Gadgets, they have been removed from the operating system. I really haven't tried to re-enable them, though I know it was possible to install a package to get something like them back in Windows 8.
There are 3rd party alternatives out there for widgets and sidebars. I'm not sure if they have all been updated for use with Windows 10 yet.
If you do a Bing search for "sidebars for Windows 10", you will get results right at the top that purport to do exactly what you're looking for. I haven't tried them and can't personally vouch for them at this point in time.