can somebody school me on injectors?

i sorta have some sense but some other questions
i understand that unlike dmax and cummins that powerstroke injectors are on the heui systema and are actuated by oil pressure correct?

so when you buy aftermarket injectors how do you know what you want?
i always thought single shots were suppose to be better and could be run without big oil
but then i see people run big oil and split shots?
so whats the pros and cons from split to single?
i am just sitting here scratching my head? (alot different from my old 12 valve)

i aint lookin at anything anytime sooner (and for sure not until i get this trans swap thing figured out)
but the education would be nice!