Show full account name - if selected, displays a user's real name next to the user's username where applicable.
This is called Set default tab in some versions of Windows.
Default Start Page - sets which tab is in focus when Task Manager is first launched.
It will, in either case, always appear in the taskbar notification area (the space next to the clock with the little icons).
Hide when minimized - if selected, will prevent Task Manager from showing up in the taskbar like a normal program.
Minimize on use - if selected, will minimize Task Manager when you choose the Switch to option, available in several areas throughout the tool.
Always on top - if selected, will keep Task Manager in the foreground at all times.
In older versions, Options is located along the top of Task Manager. This menu is called Settings in Windows 11 22H2 and newer, and is located in the bottom-left corner of Task Manager.