So I am thinking of putting hardwood in the dining room and tile in the kitchen and I would really like the floors to be at the same height (and put one of those sleek metal ‘T’ trims between them).  But I will be using an engineered hardware flooring that will not be as thick as the tile floor (underlayment+mortar+tile).  Should I just put down a layer of plywood under the hardwood and then adjust the mortar depth to get a perfect match?   If I float the engineered hardwood, do you think I would still need tons of screws in the new plywood?   If I nail the hardwood, should I use extra long nails, so they get through the plywood to the subfloor?