Did the Prophet eat at a table, and what was its height from the ground? And is eating at one considered arrogance, even with the correct posture?

The Prophet, peace and blessings be upon him, did not eat from a khawan (a raised platform with legs) nor from a high table. Rather, he would eat on a sufra or similar spread laid out on the ground. The khawan is an innovation introduced by non-Arabs, unlike the ma'ida and sufra, which are spreads for food. The Prophet's prohibition of eating from a khawan was because it was the practice of kings or the extravagant. Some scholars have inferred from his not doing so that eating from a khawan is disliked.