I'd say the floor has to be as good as it should be for putting laminate down, there are underlays to help.
Floor needs to be bob on, the clic is slightly more stable than traditional and quicker/cheaper to install.
I have only fitted C&F LVL, which isnt supposed to need an expansion gap up to 20x20m I think, I always do though and fit scotia. I think Headlams emporium click you do say it needs one.
Yes 2mm is recommended with our click, it also has fibreglass running through it which is critical for stability.