if you use text-transform: capitalize the word “stack overflow” will become “Stack Overflow”, only the 1st letter of each word gets CAPS.
but if you use font-variant: small-caps the word “stack overflow” becomes “STACK OVERFLOW” but the height of the type-face will match the height of the lowercase letters before the CSS style was applied. so all CAPS but smaller. (Sᴛᴀᴄᴋ Oᴠᴇʀғʟᴏᴡ)
and text-transform: uppercase makes it all CAPS too but but the typeface stays the same size, so uppercase typeface will be bigger that small-caps