To lap or not to lap underlayment over concrete
DO not overlap as it will cause a noticeable uneven floor when walking over the areas. We cut to size and tape where the underlayment meets. 

Overlap the wall areas and once flooring is complete prior to baseboard installation, simply cut along the edge (leaving a 1/4"-1/2" overcut) and tuck  the underlayment under the sheetrock. 

This allows an overlap of the underlayment edging and does not allow any moisture to touch the sheetrock, preventing an environment where mold can grow.