My rule of thumb, which is based on absolutely nothing but my own preference, is if the doorway has an actual door, use a transition piece, and if the opening does not have a door then let the flooring flow through without interruption. But on the other hand, aging in place / mobility people would say the fewer the transition pieces the better.

I would want the flooring to run seamlessly through the door way. No threshold guard. Just saw this in my son's home. It made the floor look cheap. They have LPV through-out and the only reason I could think they did it was the two rooms were not done in the same year so there was a "seam" to cover. Other than hiding a seam what is their purpose?

If you are getting new flooring, you don't need transition pieces from one room to another if you are using the same flooring throughout; a seamless look is best. When I had my entry hallway redone with Italian porcelain wood look tile (that transitions to my kitchen) I had no choice, but to put in a transition piece, as they discontinued selling my Pergo laminate wood look kitchen flooring (it is many years old and in great shape). Transition pieces are intended to link 2 different types of flooring.

We have our entire main floor done same flooring and transitions are used only where there is a change transition to tile (bathroom entries, laundry room), all other areas no transition piece whether there's a door to room or not because flooring runs in same direction. Much cleaner look. Purpose is tile is not same height as LPV so needs transition piece. I always thought using transition piece is because something will change at that joint.

I have a huge walk out with LVP and no transition strips anywhere but you need to follow what is reccomended by the maker . I will say we have done laminate flooring in our main floor in this house and our last one with no transition strips and had zero issues .

LVP requires transitions strips at all door openings for warranty if I recall correctly. Read the instructions.

Thanks for the advice, everyone. I’ll take that into consideration. Since our rooms run long, I had thought that running it horizontal would make the room visually appear wider - though each contractor we’ve had come provide a free quote says the floors should run length of the home. Any experience or advice regarding this?

I wouldn’t worry so much about rooms like your living room that will be filled likely with a rug and furniture, but if new flooring starts at front entry and feeds into all the rooms what do you want to see upon entering? Vertical or Horizontal. Otherwise if you have an area you want a certain direction for floor then that will dictate the remaining areas.