Assuming you're talking about facial hair and not body hair, here's what I know:
Basically the answer to all of your scenarios is yes (except maybe the one about length.) Results from laser hair removal vary widely from person to person, and really there isn't one experience that seems to be more common than others. I've had laser on my thick, coarse beard twice, and it literally did absolutely nothing, however I've seen some others on this forum say they had a big reduction in their beard growth (meaning the number of hairs was reduced.)
Much more often than not, trans women don't get the results they need from laser alone, which is why electro is considered the way to go. Being that it is expensive and time consuming, it wouldn't be so advocated if it wasn't the best/sometimes only option. You could spend $1000 on a laser package and not see any results, but results are more guaranteed with electrolysis. Even with electro, hair grows in phases, so hair will return where it was cleared, but these are different hairs that weren't active when the last ones were cleared, so you need to keep clearing until all the hairs have been zapped.
Sorry this is so longwinded, but I saw no one had replied to you so here I am. If you're talking about body hair, HRT should see a great reduction in that in areas of male pattern hair growth (back, chest, shoulders), but is very unlikely to affect the beard. If you still want to remove body hair, laser would be the most common route for body hair.