So his name was Regulus all along? Since Three Houses we knew Yuri was not his real name, merely the one he used with Count Rowe, but we did not know what this rumoured true name was.

In case you missed it, Shez' supports with Yuri involve them finding a letter between Yuri and his mother, who Yuri provides for with his underground activities. Shez reads out "Reg-" before being interupted, and later the pair look at the night sky, where Yuri points out a bright star which he says he was named after. Yuri's birthday is the 12th of August, making him a Leo (me too by the way) and the name of the brightest object in the Leo constellation, and one of the brightest in the whole sky is Regulus.

Combined with Three Houses' use of the names Sothis, Seiros and Sirius alongside the myth surrounding the "Blue Sea Star" from which Sothis is said to have fallen, it seems safe to conclude that this was intentional and, furthermore, that Fódlan shares a night sky with the real world. (I am told lots of people figured Regulus out from the names of Sirius and Regulus Black in Harry Potter, but I've never read the books so that one is lost on me.)
Some other interesting comments to be made about these stars in relation to Fódlan are that the wolf emblem of the Ashen Wolf House that Yuri led in Abyss is probably a reference to Sirius's many lupine descriptions in various cultures, as Aelfric says the name came from the star the goddess was said to come from, and that Sothis' epithet "Fell Star" seems to be a reference to the star's reputation as a bad omen in Chinese astrology.

I hope you enjoyed those astronomical/astrological observations, because I don't have much to say about Yuri's outfit. It's not bad necessarily, but I heard one person suggest that Yuri is given these garish court jester trickster outfits as a handicap to his overwhelming physical beauty or else he would just draw all the attention to himself, and I am inclined to buy into this theory. He seems forbidden to dress well...