Opening a Quark file in Indesign

I have opened Quark files in Indesign before, but I am just trying to get a little info about what makes the difference in how the copy runs.

Is it just me, or does Indesign always strip out the soft returns???

Is the main difference come from the way the kerning is calculated (specially with the new optical kerning option) or is it something else that I can control???

Any info will help, thanks.