Does the H710 series support EATX motherboards wider thatn 10.7 inches?

The H710 series of cases only supports EATX form factor motherboards up to 10.7 inches in width (271 mm).  You may be able to install wider motherboards by removing the included cable bar, however this may negatively affect the aesthetics of the case and remove some cable management options such as tie-downs that are part of the cable bar.