Remove a menu item in menu

I know this has been asked many times. But from what i got after searching, i could not understand much. I have used wp_update_nav_menu_item to add menu items programatically. But i don’t know how to remove a specific menu item. In one of the forums, it has been told to unset the array element (forum). But i did not understand it. Can anybody explain how to do it?

Do WordPress cron jobs slow down page loading?

If a user visits a site and his visit triggers a cron job that is quite intensive, the page load speed will be slower for him right? As I understand the page doesn’t wait for the cron job to execute before loading, but since the cron job would be running in parallel, it might still be the case that the page loads slower since the server is busy right?