Blast has more detail, and better performance than the default destructible. You can find some in-depth info on Blast (note that you need to be registered and logged in to follow that link).
As far as the compiled size- yep. Compiling from source results in a huge workspace. You can trim it down, but it’s ill-advised during development. I’m still wrapping my head around making “installed builds”, a similar sort of engine workspace you end up with when installing from the Epic Launcher. It’s a bit advanced/intense and a lot of work. Things break, people starve, kittens start doing drugs. So for now, I’d just get familiar with things as they are, experiment with GameWorks, and worry about that insanity down the road 