PCI slot is hardly used in modern desktop pc unless you happen to have a legacy card. Dell designed to keep one such slot to provide backward compatibility in business world.  If you don’t have such legacy card it does not matter.  Just keep UEFI at factory default.  I must admit bios navigation is a deep water and Dell does not provide in depth description either.  Bios deep dive is for advanced user only.  Most people use bios just to check boot device or storage sata operation.
Hello, We have many XE4 PCs ,when setting 1 XE4 BIOS (version 1.4.1) when press "Device configuration" in UEFI bios user interface,most XE4 show" TPV EFI Device Manager" legacy bios user interface and press 'ESC' key,it goes back to UFEI bios user interface. But I don't know what I've done and make one XE4 to show all Legacy BIOS setting user interface, Please see the following pictures, Left one is UFEI ,right one is legacy ,(Why BIOS 1.4.1 not support legacy user interface?) 1.4.1 UFEI user interface is the worst one I've ever seen. font size is too small to ready and loading is heavier and slower than legacy one. Is there any tip to show this legacy user interface instead of UEFI one? Don't tell me it's a bug, I prefer legacy user interface than UEFI one. [IMAGE] [IMAGE] [IMAGE]   [IMAGE]
How to make Optiplex XE4 BIOS from UFEI mode to Legacy mode?