When you are showing a person how to use WordPress for the first time it is a good idea to make them an Editor role instead of an Administrator. You can use a plugin called Capability Manager Enhanced to give the Editor Role more than its usual permissions.
By default the editor cannot edit widgets, theme options, page builders, slider plugins or other types of plugins. The user manager plugin can give an editor access to many of these.
Note that editors can see all users, but cannot create other editors. They can only create users at the author level.