When I am using a CA at close to mid range I often switch over to AP shells and just score a lot of nice full pen AP damage on a Republique, long range I target a Republique a lot with with HE for easy fires. I actually would take a secondary build Yamato into a brawl before I would do so in a Republique there days because of how soft Republique armor is. Republique gets it’s own captain thanks to its secondary guns only being good short term, and actually often just ending up as AA protection I would go for survivability build with AR worked in to help rate of fire, but allowing for maximum management of fires.

So I actually now have a captain that jointly serves Normandie as I really like that ship and does well with BFT / AFT secondary build that it shares with JB. JB secondary guns feel like they do better, less chance of being set on fire, and armor feels stronger. Only Warships a I have felt safe using the secondary Armaments mod on is Yamato and Musashi thanks to their very heavy main turret armor, and the fact their secondary modules are in need of added durability.

Plus you can’t use secondary armaments protection module as your main gun could get destroyed instead. Secondary gun mounts tend to be very fragile on Republique as well as much higher chances of catching fire as well as weaker armor.

French battleships in world of warships