Is it reasonable to have a low ceiling on the same floor?

The design of this kind of drop ceiling is very common, because the function of the ceiling is to form a height difference in addition to arranging the light strip and blocking the beam, so as to create a sense of visual height and hierarchy. All the same height ceiling is better than not to make a ceiling.

You don't see the full effect in the picture above.

However, it is more common for the ceiling to have a height difference, and the key is the overall effect.

Judging from the picture you sent, you want to add a small bar at the beginning of the stairs to pull it over and then connect with the ceiling in the living room on the right, this idea is normal.

But it's not reasonable, and it depends on how the ceiling designer on the left deals with it. If there is no other treatment on the left, just above the hall (the right side is estimated to be the location of the hall), it seems ugly.

Look at your picture, if this top is made and painted with latex paint, it is still very good, if you feel that the top surface is too different, add a plaster line, it can be weakened a little, and it will not be so eye-catching.

The renderings should be able to be represented, so that there is no problem with the design, and the designer must be trusted.