I don't really know much about a sword and shield style but what I do know is that with the right timing, you could potentially knock an opponent's sword out of their hands by parrying with your shield
I have fought with a sword and shield once, I was fighting against my brother, he had dual shortswords and I had a longsword with shield, I was able to block multiple hits and take him down
In my opinion, I don't get why people made shields smaller, I totally understand why the spartans had medium sized shields but the vikings, why couldn't we stay with tower shields