Build stealth sniper for IJN BBs, but in the last module of the equipment, the unique update of the Yamato (legendary module) is selected, in the case of ships like Musashi and Shikishima this option doesn't exist, so it is recommended to put the reload reduction.
About the captain's skills it's recommended to use captain Isoroku Yamamoto, as he improves the turret rotation of these ships, otherwise their turret rotation will be very slow, so it is almost mandatory to use the Yamamoto.
About Yamato with this build, the values are:
180° turret spin - 55.7 seconds
maximum horizontal dispersion - 239 meters
maximum vertical dispersion - 191 meters
cannon reload - 30 seconds