Why did Lavan answer before his father Besu'el?
Rashi: Because he was a Rasha.
Ramban (29:5): Because Besu'el was a nonentity.
Ha'Emek Davar: He was a Rasha, but we also infer that Lavan was primary in the house.
What caused Lavan and Besu'el, who were idolaters, to acknowledge that Hashem had orchestrated the above-mentioned events?
Rashi: They realized the truth due to Eliezer's portrayal of the events that had transpired. 1
What is the significance of the statement "me'Hashem Yatza ha'Davar!"?
Mo'ed Katan, 18b: This teaches us that Shiduchim are made in Heaven. 1
Malbim: Since it was miraculous through Hashgachah, and not through Mazal, we have no free choice to oppose the Hashgachah.
What did they mean by "bad or good"?
Rashi: They meant that they were unable to refuse using foul means (via a harsh answer) or fair (via a straight, logical one).
Seforno and Rashbam: they could neither refuse nor uphold the Divine decree (which did not need their acknowledgement). 1
Rashbam: Seeing as, with or without their consent, Hakadosh-Baruch-Hu, put His plan into action.