He's about 2 metres tall. In one of the trailers he's fighting with Noctis in some tunnel.
Where are you getting a fantasy European vibe? XD As a European most of the game looks actually like the US, Southern America (Duscae, the desert, Lestallum) and Japan (Lucis and Insomnia) to me. Though since Kingsglaive they seem to be shifting the tone more to alternate medieval Europe, that is true.
As far as I know many of the monsters, including this undead samurai, are from older Final Fantasy games, such as 5, 6 and 7. They wanted to give some fan service to loyal fans.
The craziest design is imo this...thing:
D:
Or that horrible spider lady that I can't find an image of at the moment.