In retrospect, the laminate flooring should have been continued to abut the tile and door threshold. If you're doing this yourself, and still have some material left, the transitions in A and B could be bridged with another piece of laminate, ripped down to the proper width. C is more difficult, because the boards are cut off and perpendicular to the tile, and you can't lengthen the boards retroactively to meet the tile (but keep that in mind for your next job). If this isn't possible, then do what stonetech said, and get a couple reducer strips.

I did both. I was taught by an installer how to flush cut the flooring to butt up against the tile, which did have an edge strip, with a 1/16th (I think, it’s been almost 2 years) gap and silicone caulk. I hated it because the flooring is matte and I couldn’t find a caulk that wasn’t shiny so it left an obvious shiny line between the tile and the laminate flooring. I replaced it with a transition strip. I do remember messing with the strip to making it as flush as possible between the two different floorings, I think we had to modify the metal piece inside or route one side deeper. keep in mind all of this was DIY and with proper planning by a pro installer the different floor levels are taken into account. I changed my mind and decided to tile the powder room when the flooring was already in. Also, in this scenario the ends are supposed to be sealed and caulked beneath the transition strip in a powder room application, even if it isn’t “wet,” like with a shower or bathtub. That was so deep in the specifications for the flooring we almost missed it. I did not use a transition strip by the front door. I intended to, just to be cautious since we spanned a greater distance, but I hated how the strip looked. Next to the threshold the caulk is invisible, even though it’s shiny. We were pressed on time and budget because it was a new home without any closet shelves, garage storage, or landscaping. The idea of replacing the carpet that was falling apart (after less than a year) with more of the same carpet by the builder was discouraging to me, so we really couldn’t do anything differently. But in a more predictable world, if I could have wrangled a couple thousand more, I have done a simple, not engineered, hardwood and installed it ourselves. The laminate has not had any issues at all as far as buckling or drifting. It’s on our main floor and the only place with an issue is where my kids drop ice cubes on the floor in the same spot and don’t pick them up. There isn’t any swelling or peeling but there is a thin line where you can see the composite is a different color. This is not in an area with a long span. The LVP with equivalent numbers of pieces were 2-3 times as expensive.

You can purchase uneven T-mouldings for the areas where the floors are not a matching height. That is normally the way it is done. As for direction of laminate, you have a close match to what already exists but it isn't a match. Changing directions is about the only way this will look OK. A diagonal install would look REALLY good, but it will require 15% - 20% waste which you may not have enough on hand.

An uneven T-moulding can handle 3mm of variation between two floors. But 3/8" is too much for an uneven T-moulding. That means a reducer would have been the better option. Is your GC a flooring expert? Does s/he KNOW a flooring installer? A handy(wo)man will have many resources but not all of them will be professional grade. A floating floor that is sitting 3/8" (9mm or so) higher than an existing hardwood/permanent floor is a big ask for anyone other than a flooring professional. One thing you can do is reach out to door and moulding company to see if they have any reducers, L-stops, etc that will work with your existing height variation. You will probably have to have them mill something for you. Which they can do...for a price. While they are at it, go ahead and get them to stain it on site as well. Send in an off-cut of your marmoleum and get a slightly darker stain match. As in clothing seams, a transition piece looks better if it is darker rather than lighter (if they cannot get a perfect match...which they can't). As a heads up, it could cost $70 - $100 for a 6ft piece. Question: did your installer seal the seams of the click together laminate for use in a kitchen?