The one answer to my previous question suggests that all Illusions conjured by Disguise Self and Seeming can be seen through by the user, but not by outside viewers.
The two spells Disguise Self and Seeming both differ from traditional Illusion spells in that they contain no clause that causes the Illusions to "fade" or "become transparent".
Instead, successful Investigation checks allow viewers to "discern" and "become aware" that the target is disguised.
Can viewers succeeding on the check literally see through the disguise? If a Half-Elf disguises their race to look like a Drow, does the viewer know their true race if their check beats the disguise, RAW?