The BUFG_GT/MBUFG_GT buffers can drive any loads in the fabric and include an optional divider you can use to divide the clock from the GT*_QUAD. This eliminates the need to use an extra MMCM/XPLL/DPLL or BUFGCE_DIV to divide the clock.
Clock Regions with GT resources also have direct access to a DPLL resource you can use for frequency synthesis and clock network deskew.