Some are slightly more necessary than others I think.
Like when I see a book and it has "X Title a Novel" on the cover. I think "a novel" is pretty redundant as I see novels as the default thing a book can be.
As for anything that isn't a novel, like anthologies, poetry collections, what have you, then I would include that. Having "An Anthology" after the title would better prepare a potential reader for what to expect.
For "The", I don't really care either way for them. But for my own works, I generally don't use a preceding 'The' since listing things alphabetically can be annoying, so I rather just have an active word as the first word of the title.
For subtitles, unless the whole series is just going by the main title, I find them unnecessary.
Most of the time, I will only use flourishes for promotional purposes, to further specify what my story is about for potential readers. Like "check out my novel Secunda, an erotic historical fantasy monster romance."