Why does it say "Yodu Shimcha"?
Radak: Then all nations will thank Your name, for it is "Gadol v'Nora."
Malbim: They will not thank Him Himself, only His name. Thanking the name implies that they heard from afar, but did not attain Him Himself. They know of Him only what was publicized from His deeds in Tziyon - His Hashgachah.
Why does it say "Gadol v'Nora Kadosh"?
Malbim: He is Gadol, Nora and Kadosh. These refer to the three conducts in these three Mizmorim. Gadol - He is the First and Last cause. Nora - He can arrange a framework, and override it to agree with His conduct. Kadosh - He is elevated above the regular conduct via nature. He does wonders with His right hand and His Kadosh Zero'a, in a miraculous way above the laws and orders of this world.