I am double posting this (from Design Dilemma) because I hope for professional flooring advice and also suggestions from people who've done this.

We live in the Pacific Northwest (rainy winters and dry summers). Our house is 13 years old with ¾” OSB subfloors on joists 16” on center. We want to
remove the carpeting in the dining room, living room and hallway (above grade) and downstairs hallway (on grade), and replace the carpeting with wood flooring. We also want to keep the height
difference between these rooms and the adjoining tiled kitchen to a minimum. Because of this requirement, I am leaning towards 1/2" engineered wood rather than solid 3/4" wood. The new flooring would be professionally installed.

Am I correct to say that OSB does not hold nails/staples as well
as plywood for nail-down installation, nor does it provide a
suitable surface for glue-down engineered wood flooring installation? Would glue-down installation avoid the squeeky-squeeks that might result from a nail-down installation? We have heard that installers recommend
having an underlayment put down over the OSB to provide a better adhesive surface for engineered wood flooring and we would have that
done.

I don't think a floating floor would be an option because of the upstairs room size (50' x 15') and high ceilings (possibly too noisy).
For glue-down engineered wood flooring, what
underlayment would be best between the OSB subfloor and the engineered wood
floor? How thick would it need to be?

Thank you

Mary