One possibility is that Japan does not withdraw from the Treaties, less likely they remain in the LON, but if they accept numerical inferiority to either the RN or USN and instead assume they can pursue technical superiority then I think it is a huge shift in mindset. I think the later course hastens Japan's economic woes, so it seems smarter to let the Treaties constrain opponents who can up build you. Even if they leave the Treaties they will pursue superior ships unfettered by ship tonnage limitations. In the former scenario I think one sees every advantage pursued in the limitations, in the later I think you see larger ships.
Without the war in the Pacific I think the battleship holds its place as "the" weapon longer, but I firmly believe that in both the USN and IJN it was becoming obvious that the battleship was being eclipsed by the carrier for its ability to project damage at range and speed, the naval gun had reached its upper limits, as the next generation of aircraft came into service, especially on larger carriers, it will be the carrier that becomes the foremost capital ship by the end of the 1940s. I think the big guns had a little more life in the Atlantic and even the Med since aircraft will take a little longer to evolve better all-weather capability and in the Med one might still see many assumptions about land-based air power negating the carrier as a strike platform but its fighters should see a sharp rise in importance. That means the RN stays its course and develops armored carriers with smaller air groups. The IJN, like the USN, likely pursues bigger air groups with larger strike aircraft complements, more capability in its aircraft overall, all push up carrier size.
The IJN as far as I can tell relied more on force of personality and combat experience to drive innovation, it seems to lack more formal institutions, so that is the wild card. I think the Japanese pursue the aircraft "carrier" submarine as a stealth raider / "cruiser", but the sub arm should remain committed to striking the enemy fleet. The big gap is electronics, the Japanese need to develop radar and sensors, if they do not get serious about it they may remain technically deficient in that realm longer. Without fighting the USN they may not appreciate the problem until they get trapped playing catch-up, relying too heavily on traditional skills in things like night fighting.
The Japanese had a better land-based naval air arm and better doctrine, I think they continue that, and they had excellent sea planes, another area they will develop out. Japan has a thinner industrial base, it played its hand well up to the eve of war, here they need to jump past the 1,000 HP base line engine and pursue the 2,000+ HP, and of course we do not know when jet engines appear but I suspect they get caught a generation behind there too.