Thanks for all your responses. 1. I will replace the door casing once I am done dealing with the transition issue. 2. The problem with the transition piece and its resolution depends a lot on whether I can safely remove the piece - I installed it (and the tiles about 8 months ago) so it certainly is firmly seated. So, is it possible to remove it, without doing much damage to the surrounding tiles? 3. If i can remove it, then I want to proceed as follows (please see figure below for directions): . (i) Once I remove the transition piece, I will extend the tile from the bathroom (I still have extras left) by 2" into the doorway (see "A" above). (ii). Note, the laminate planks were not finished evenly either .. "C" is a bit wider (about 1/2", while "D" is a bit tighter, about 1/8". So, I will first straighten the laminate ends by trimming it evenly at the "C" level. (iii) Extend the laminate tiles to cover "B", using a 2.5" horizontal plank. (iv) Alternatively, I will just replace the marble transition strip with a slightly wider one (about 4.5"). (4) But If I am unable to / or it is not advisable to remove the transition strip safely, then, I will even out the gab between the transition, and the laminate tile, and use the caulk as suggested to cover any residual gaps. thanks again and please, let me know your thoughts on my plans thanks - Oyiwaa

I see two options. The first is to have your tile person straighten out the edge of the tile. Fabricate a reducer that's 1/4" thick i.e. the difference between your wood and tile), finish to match the floor and cut it to length. Undercut the door stops to the height of the tile so the reducer will slide under. Fill the gap between the wood and tile with something that's the thickness of the wood. Apply a little construction adhesive to the bottom of the reducer and install it, weighting it down until the adhesive dries. This can be done by closing the door and sliding wedges under it. The second option would be to use a matching baby threshold that would lip over the tile and hide the uneven edge. Fit it, fill the void, undercut stops and secure with adhesive. Trim the door bottom if needed. The bottom of the baby threshold might have to be shaved off so it sits level. If it's made for a 1/2" floor and your difference is only 1/4" you'd have to shave off 1/4". The first solution yields the lowest stepover height but is more work. The second is easy but has a bigger hump at the doorway.

Your plan will fail. All decoupling membranes do is decouple. They do not add any additional stiffness. Winderboard is a decoupling membrane, and would need a layer of thinset underneath it to even perform that job. It does zilch for creating a stiff enough subfloor suitable for tile. How to find someone who knows something. https://www.ceramictilefoundation.org/homeowners-guide-to-hiring-qualified-tile-installer This is the industry bible that will tell you everything that you need to know. https://www.tcnatile.com/products-and-services/publications/218-english-publications/188-handbook/957-2018-tcna-handbook-for-ceramic-glass-and-stone-tile-installation.html

I did my wood to tile transition without strips (in order to make my place more handicap-friendly.) They just have to make the top surface of the tile and the top surface of the wood be the same height, I think I have about 1/8th inch difference at most between kitchen and living space, no difference between hallway and bath, and 1/8th difference at most between master and master bath. Back at my old home, I had a transistion strip between the dining area and the kitchen - it made it horrible to move from the linoleum of the kitchen back out to the wood of the dining area when I had a broken ankle and was on wheels. Plus the strips really do look ugly. (PS< the wood transition strips look fine, but mine were metal strips... but neither are necessary.) Others have pointed out you can have hardwood throughout, I just simply didn't want to do that. (Actually, my wood floors are broad beam pine, which is soft, anyway.) My build is semi-open, so I had the option in the kitchen to do tile, and so I did.