The King George V design was a political compromise

Could the King George V class have carried larger guns or triple turrets?

Yes, but the 14-inch decision was a political and treaty-driven compromise rather than the only feasible technical solution.

Technical possibility differed from the practical ship Britain chose to build. Fifteen- or sixteen-inch alternatives were viable, and British work on Nelson, Rodney, and the G3 studies supplied usable triple-turret precedents. A King George V-type hull could therefore be redesigned around fewer, larger turrets instead of the historical quadruple 14-inch arrangement. The class that entered service reflected treaty diplomacy and senior political preferences for 14-inch guns rather than the outer limit of British engineering.