Would + ing

You would be crying if I were there.
I would be doing it if I were there.

I should've been talking to her if she had seen me.

What do sentences like these mean when they are in second conditional?

A: We would be playing if I were there.
B: I would laugh. - BTW, why didn't the speaker use the version with -ing?
A: You would be having fun.

Should I keep using versions with -ing once I started explaining a particular situation?