If your slab as wet as your described, I would certainly recommend to use MVP or something similar to seal it first, then Floor Muffler, then float your engineered T&G floor on top. I want to talk a more about your floating T&G engineered flooring. These types of multiply engineered wood floorings are usually designed for glueing down application when solid hardwood flooring are not suitable to use, such as in a condo project,basement or main floor slab subfloor. So the tongue and groove are usually not milled tight enough to hold the T&G in place after the edge gluing. So the boards will tend to separate before the glue dries. If it is random length products, installation will be even harder with some boards are shorter. However most of the engineered flooring brands allow to float their flooring to cover more market or applications. To me it may not be a good choice for DIY home owners simply because they are not as easy as the traditional European style longstrip 3 ply floating wood floors to install. Even without Click Lock system, a T&G 3 ply engineered wood floors are very tight to tap the tougue into the groove. So when glue applied in the upper part of the groove, the tongue will stay tight once tapped into the groove. I guess this is the difference between an engineered wood floor and an engineered floating wood floor, which we are asked all the time by confused consumers. So the answer to your quesiton is: If the tongue and groove is tight, you can edge glue without using the strap. If not, you'd better strap them.I hope my 2 cents will help.

I'm pretty sure they don't sell Kahrs at HD, but perhaps the OP was just shopping for underlayment at HD? Anyhoo, I'm also interested in hearing from others who have installed Kahrs floating over concrete. I'd like to hear about the differences between the Kahrs Combo 2-in-1 (blue plastice with tiny foam beads sandwiched in between) and the Floor Muffler. We're installing the 5/8" thick Woodloc. I'm thinking it's thicker so maybe the Combo 2-in-1 would be sufficient. Seems like the Floor Muffler/foam underlayments get recommended most often when installing thinner laminate flooring. But maybe I'm wrong? I do know that I don't want to hear plastic crinkling everytime I walk on the floor, as another poster mentioned!

Not an expert-- still working on these issues myself-- but I think that with gypcrete below and engineered wood above, you could have pretty much any underlay you want without worrying. You are getting great efficiancy from the choices you've already made, and the underlay is such a [relatively] small part of the equation that it won't be a problem.

The most important thing im going to mention involves the concrete flatness/moisture just by looking at the concrete is not good enough to deteremine flatness...take a 7ft straight edge and get on your hands and knees and check EVERY square foot. guarantee there will be higher and lower spots. spots that need to be addressed prior to any work regardless of glueing or floating the wood. then while the water drop test is a good start. you will need to check the moisture level of the concrete. the last thing you want to do is spend all the work laying the floor only to find the floor buckled a few months down the road due too high moisture, then having the rip everything out and be stuck with wasted time and money.