david1995 :
Will the 2GB bigger one fit
Any PCIe x16 card will work. VRAM size shouldn't have anything to do with its physical size. Length will be the only limitation. If in doubt, check the card's length in its specs and then measure the distance you have in your case from the expansion slot covers to the first obstruction you come to; usually the drive cages. But most GTX 750 or 750 Ti cards are pretty short.