Why does the Torah need to tell us that they were the ones who spoke to Pharaoh ... ?
Rashi: They were the ones who were commanded and they were the ones who carried out the commands.
Seforno 1 : And by the same token, they were the ones whose words would be accepted by Pharaoh.
Why does it repeat "Hu Moshe ve'Aharon"?
Rashi: To teach us that Moshe and Aharon maintained their level of righteousness from beginning to end. 1
Rashbam (in Pasuk 26): The sequence of this Pasuk and the previous one teaches us that although the Torah switches the order of their names, 2 they are the same two people.
Targum Yonasan: Moshe was the Navi and Aharon, the Kohen. 3