I don't think I've ever seen more than 4 8th notes beamed together. I think 2 vs. 4 beamed varies. In 6/8 3 notes are together. It sure makes counting & subdividing the beats easier.

With vocal music the slurs indicate that all notes are one syllable. 8th notes beamed meant the same as a slur and separatly noted 8th's would mean different syllables. I've seen music recently where 2 notes are beamed even with separate syllables. It's really confusing. I wonder if it's instrumentalists writing the music or music notation software programs that won't allow the separate notes.