[jimbo2012]

I think glue, but you're supposed to have the concrete moisture tested first if it's a an older home.

I guess the floating floor may make noise with shoes due to the air space below.

I'm no expert on that.

A friend has the floating floor over a mold resistant pad, it just isn't the same feel, and seams open up from time to time.

But in my current home, I glued the 3/8" to plywood subfloor, 20 years no issues.