Who are "Yir'ei Hashem", "Zera Yakov", and "Zera Yisrael"?
Rashi (23, from Shocher Tov #1): Yir'ei Hashem are converts.
Radak: They are Yisraelim. Also elsewhere, they are taught separately - "Beis Yisrael Barachu Es Hashem Beis Aharon Barachu Es Hashem; Beis ha'Levi Barachu Es Hashem Yir'ei Hashem Barachu Es Hashem" (135:19-20) - each blesses according to his level, intellect and closeness to Hashem.
Radak (from Shocher Tov #2): Yir'ei Hashem are Kohanim. "Kol Zera Yakov" are Leviyim. "Kol Zera Yisrael" are Yisraelim.
Malbim: Yisrael is a higher level than Yakov; Yakov refers to the masses.
What is the meaning of "Guru"?
Rashi: It is an expression of fear.
Which group should honor Hashem?
Radak: Honor is love. Yir'ei Hashem will go from fear to love. "V'Guru Mimenu" was said for those who did not reach the level of Ahavah 1 .
Malbim: Yir'ei Hashem will praise, and the others will hear. "Zera Yakov" will honor; this is a lower level than "Zera Yisrael", who fear. Honor is because He is the First Cause and conducts nature. Fear is recognizing Hashgachah Pratis to bestow reward and punish.
Sotah 31a: Serving from love is a higher level. Hashem guards Bris and Chesed for 2,000 generations for Ohavav, and only 1,000 for Yere'av. Rashi there says that this refers to fear of punishment. Nesivos Olam (Yir'as Hashem 1) says that it is even for Yir'as ha'Romemus. Rikanti (Bereishis 22:12) and others hold that Yir'as ha'Romemus is greater than love.)
