How far ahead was Kii's technology in 1918?

Would Kii-class battleships be more advanced than the technology Japan understood in 1918?

Only somewhat: the design belonged to the planning horizon around 1921, so much of its technology would already have been understood or under development.

The design is placed only about three years beyond the scenario's 1918 starting point. Its intended technology would therefore be advanced in some respects without being wholly unfamiliar to Japanese designers. Much of it was already on the drawing board. Its large battery of 5.5-inch guns also means an attacking destroyer force would face substantial defensive fire.