I'm helping my in-laws with unglued tongue in groove laminate flooring. there is a minimun 3/8 to 5/8 inch space required. The sheetrock doesn't reach the floorand the gap is large enough for the flooring to fit under. Will it cause a problem to have a larger space by going in front of the sheetrock. We don't want the flooring to shift.
Also it says to seal the cement and then put down a vapor barrier, is the sealant a must?
The recommended gap is between the flooring and the nearest obstacle, in your case, the framing behind the drywall. To answer your question, it wouldn't necessarily HURT anything to leave the gap from the edge of the drywall as long as it will be covered with base, but I don't think it's necessary.
As far as the sealant: It's not a must....unless of course you want to keep the manufacturers warranty in force. They will look for (and find) ANY reason not to pay off on a claim, and any deviation from their instructions qualifies as that reason.