Although “random nonsense” vocals kind of grind my gears in theory, it tends to be very difficult to make out the lyrics from an epic choir with orchestra, so I still settle for random syllables for the most part.
Best effort/results ratio I’ve seen so far is with Performance Samples Oceania. [https://performancesamples.com/oceania/] Just play chords for instant awesomeness, basically! There are keyswitches to select syllables and control ‘s’ endings in a consistent manner (so it doesn’t differ between plays/renders), but I usually just try some different starting points and let the syllable round-robins run.
If I want actual lyrics, I use EastWest Hollywood Choirs, which has a full set of consonants and vowels, and a phonetic sequencer (syllables + piano roll editing with envelopes for tweaking) to go with it. It’s a fair bit of work to actually get it to do what you want, but you can get pretty amazing results. Haven’t done any serious projects with it yet (I need to write lyrics again, for starters…), but played around with it some time ago: