Both G75's and G750's use MXM 3.0b cards/slot.
The only difference between them is the way the vBIOS is implemented and their ROM sizes.
Since the vBIOS in the G75's are part of the system BIOS (88KB) they cannot be dumped using NVFLASH like how the G750's (163KB) can, since their v/BIOS is located on the card; This means more user control over the clocks and voltage. Also, raising the OC limit +135 is the same as done in previous generation cards, as is voltage range/stepping and P-state clock control.
On another note, KBT works on all G750's cards, where with the G75, it cannot. So just raise your clocks this way.
You can use standard MXM 3.0b cards in the G750 given the right chassis/heatsink modifications to fit, as it will run out of the box unlike with the G75's, as further modding is necessary.
There are more differences between the ASUS G750 cards and the MXM standard than just the PCB layout. However, this does not affect using a different card altogether.
I'd recommend just upgrading NB's if this is your first time modding rodeo, as likely things begin to get expensive if going for trial and error.
