My wife and I are remodeling our kitchen, and our contractor ask us if we want to remove the hardwood in the kitchen. He said that keeping the hardwood will make the floor solid. I did some research online on tile installation with existing hardwood, and most say to remove the hardwood because of the possibility of existing defects and warping nature of the element. So, I requested that the hardwood to be removed and asked if there are shortcoming with removing the hardwood. He said that the floor will feel a bit "softer". I didn't mind a "softer" floor if it was just the texture. I didn't know and not informed that a soft floor can lead to less durability and cracking on the tile floors. I didn't learn about it until I did some research after the contractor said the installed floor (tile->cbu->plank subfloor) is too soft. So, now, we have to pay extra to have him remove/redo the floor installation. What disappoints me is that most suggestions online say that an exterior-grade plywood is needed for plank subfloor and that wasn't brought up. And, that a soft/vibrating/bouncy floor impacts the longevity/durability of the flooring.
So, here are the questions. What plywood should I use to promote the best longevity/durability of the floor? (I see CDX, BCX... and 5/8") Is it better that the plywood has tongue and groove? (I went to Home Depot and cannot find BCX or CDX plywood with tongue and groove. I see DryPly and other plywoods, but I couldn't find a X-rating on those plywoods.) Should I keep the hardwood and install tiles/cbu on top of it for my other kitchens and bathrooms? Is tile, CBU, plywood, plank subfloor sufficient for the flooring in kitchen? Bathroom? (I didn't see waterproof material between CBU and hardwood in the bathroom.)