You can set individual brackets using "left" and "right", but the distance between the brackets will not be fixed, as they adapt to the argument. Nevertheless, there is a way to display brackets so that the distance between them is fixed. To accomplish this, place a "\" (backslash) before the normal brackets. These brackets now behave like any other symbol and the alignment is the same as with other symbols:
left lbrace x right none
size *2 langle x rangle
size *2 { \langle x \rangle }