The case has a maximum GPU length of 345 mm. Note that if you mount a radiator in the front of the case, you will need to lower the maximum GPU length by the thickness of the radiator.
If you, for example, would mount a Celsius+ S36 in the front, which has a thickness of 30 mm, the maximum GPU length would be (345 - 30) 315 mm. If you also plan on doing push/pull on the radiator, remove the thickness of the second set of fans too.