Scarpa

Hi guys, Looking to place some engineered oak flooring throughout the downstairs of my house and have a few queries. The internet seems to show different ways of doing thing. The sub floor is pine boards over joists with the kitchen being a concrete slab. I'm looking to float the floor so I can use a good quality insulating underlay. 1) Do I lay the new boards parallel or perpendicular to the sub base boards? 2) I am probably going tongue and groove style. Do I glue the boards together? I've seen youtube videos showing them being glued together and then I have seen big high street chain stores video tutorials showing them not being glued. Can the floor still expand ok if its floating and glued? 3) How do I approach the sub floor transition from suspended timber to the concrete slab in the kitchen? I would like it to be continuous. Is this a bad idea? many thanks