Can Awz and Khazraj be considered as ahlul hal wal 'aqd? Does it include the muhaajiroon as well?

No, ahl al-hal wal `aqd refer to those who have power and are influential in terms of decision-making in the Muslim state.

To understand who the Ahl ul-Hal Wal Aqd are, we must look to the very first Ahl ul-Hal Wal Aqd that existed in this Ummah. From studying the Seerah, we know that they were from the people whom the Prophet (ﷺ) accepted Nusrah from – the people from the tribes of Aws and Khazraj. These were the Sahaabah (muslim) who are described as the Ansaar and the Ahl ul-Hal wal Aqd were the leaders, influential and representatives of the whole Ansaar whom the rest of the Ansaar would obey in their decisions.