The triangles indicate connecting rooms.
We had no problems being at the stern of the ship - it was actually very nice because it was just a short walk to topsiders for breakfast. We were a little worried about noise because we were right under the deck outside of topsiders, but we only heard an occasional chair being moved by the staff early in the morning, and we were up before the time that the hordes decended on topsiders. Beyond that, I don't think it really matters much if you're at the bow or the stern, but I've not experienced the bow (next trip we'll be just off the forward elevator lobby on deck 6), so cannot say for certain.