Husqvarna chainsaw questions

So I’ve got two Husqvarna chain saws. 5 years old 450e 18” blade and my brand new 562xp with a 20” blade.

There are a few types of chains for this- a low kickback and a more aggressive chain. What is that more aggressive called?

also the 20” blade on the 562xp needs to be longer. I was going to go 28” - how do you figure out what is the correct blade and chain for a 28”?
Current chain and blade is 3/8” .058” 72 link.
I want to go longer but not sure if longer changes chain width and link size or does it just mean more links.

I’m not new to chainsaws, but I know there are better resources than just dealer for parts.
Thanks,
Joe