Bottom Line Up Front (BLUF): Suno V4.5+ is an extended version of the 4.5 model. It keeps the familiar sound but follows complex descriptions better and builds long tracks more carefully, so it suits songs whose idea must survive from start to finish.
The plus version adheres more precisely to a detailed description: several instruments, a shift of mood, a specific vocal type. Where the base 4.5 might "simplify" an idea, V4.5+ more often sees it through.
Simple and custom modes are available, as well as an instrumental without vocals and your own lyrics. The finished track downloads right away and the duration is up to you.
It is an improved version on top of 4.5 — pick it when you need precision for a detailed description.
Yes, the model sings in various languages; the language usually follows your lyrics and description.