Kaijuformers, Kaiju Transformers, is what you get when one side of the war decides to ramp things and the other follows suit to survive. Should it start on the Autobot side then mostly blame the Matrix of Leadership for its decision to turn Optimus into a giant monstrous titan at some random point. The reason why or whether its permanent depends on you handle the eldritch Spark containing pacemaker.
If it occurred on the Decepticon side first, then it's fucking Shockwave whose at fault. He did make actual Predacon clones in Aligned and took over Onyx Prime's body in the comics. There's a reason why the phrase "There's Satan and then there is Shockwave" exists. Megatron just approves the idea.
Either way it would be pretty fucking scary when you think about this iteration of their war on Earth. Literal giant monster fights that is just as destructive like in actual monster movies. There would be new technology created to make this new style of war more unpredictable.
Battleground Generators that form a temporary alternate pocket dimension to avoid massive unnecessary damage or unwanted casualties. Stealth Fields to make attacks undetectable unless intercepted in time.(You know the cases where entire towns or colonies of people disappear with no explanation on their whereabouts. It's like that but as a hunting ground based attack.)
A species known for adaptation potentially taking things a step too far. Decisions that could ultimately change Cybertronians into something unrecognizable from their original forms. War is terrifying for many reasons as morals barely matter and there are no lines left to cross.
Is it really worth it when the only way forward is to discard what you once were for the power of a monster?
Edit: There's nothing Godzilla related here. I just put the GIF here cause I thought it would fit. Lol