Prep - all the floating floor specs I've ever read call for no more than 3/16" out of flat and level across 10' (for every floating floor, not just laminate), so you'll need to do some patching and leveling even if you can scrape out all the old parquet. If you install your click flooring on an uneven substrate, the finished floor will feel springy and sound hollow, you might be able to see it move when you walk on it, and the t&g joints will be stressed by the movement and will eventually fail.
Pad - good separate pad will have an integrated moisture barrier, will have published IIC and STC (sound transmission) ratings, and will make the finished floor sound better.
Product - I'd avoid laminate entirely, and use a WPC-type floating luxury vinyl like Coretec. It's a hot new trend, and every distributor and his grandma has a line of it. Laminate (with a few exceptions) is easily damaged by moisture; WPC click vinyl is waterproof. It's also slightly quieter and less "clicky" - sounding than laminate, though a laminate installed over a well-prepped sub with a good-quality separate pad shouldn't be particularly noisy under ordinary foot traffic.
You mentioned that the flooding problem has been dealt with, but in multifamily construction there is always the chance of more flooding. I know several contractors who do nothing but rebuild water-damaged condos in the Seattle area. Someone's dishwasher (or icemaker, or washing machine, or...) supply line is always breaking and leaking while they're on vacation...
More to the point, surface water like a dog dish, a spilled drink, even a sweating grocery bag with frozen goods inside can damage a laminate floor. The core is just dense fiberboard.
Just like painting, just like PugetDude said, the prep work is the backbone of a successful install. I'd look at Ardex or Uzin for prep products if they're available in your market, they both make a dizzying array of patching and leveling products.
Good luck!
JR
