Re: All three scenarios would (respectively) apply, Adam.
[Hence... too many theories and not enough data. Have to keep looking.]
Yes, always. lol
[Or Woolfson's Capture Hypothesis suggests that instead of capturing planets (formed in disks deformed by stellar near-misses in high density stellar nurseries) red dwarfs will tend to lose them. Hence OGLE finding seemingly plenty of brown dwarfs/ free-floating planets.]
L and T type dwarfs may very well fit in that scenario.