First let me say bravo you! You’re smart, catch on quickly, and ask great questions. All the makings of a promising Hunter!
Bad Hunters are lazy, think the spec is far simpler than it actually is, fail to have vision to see it’s complicated potential, and think they know everything. (Why wouldn’t you want to over-excel while playing the most mobile Class/spec in the game?)
As you can see by the various answers on pets, there’s a wide range of choices/preferences for various circumstances. Again, whichever suits your play style and you find the most fun, are the right choices for you.
And yes, Pet Taming is a game of it own, because it’s a very integral part of the spec that is very personal.
There’s a reason why there are five on-board stable slots at max level, and an additional 200 at the Stable Master. (Plus, Divas like me prefer my pets match my mogs - or mogs match my pets.)
I’m going to be an additional outlier - but then I solo mostly. I prefer Spirit Beasts because of Spirit Mend. It’s a great additional heal with a shorter cool down than Exhilaration, and handy when Exhil is on cool down.
I turn off the auto-cast, so I can make it on-demand. Just make sure you are the focus before you cast it.
It can also be cast on any friendly player even if you’re not in a group, (or NPC in certain circumstances like in the BFA Warfronts.)
Remember: BM Hunter gets more complicated (harder) the more active talents you allow yourself (and your pet.)
Also, every pet model moves/paths differently depending on animations, and abilities.
Have Mend Pet ALONE (independent of the pop-out pet command menu) either on a keybind, or an easily clickable action bar slot - you need it a lot. You can also macro it with other things, but it’s good to be at your disposal when needed, (especially since they extended Revive Pet’s cast time. Grrrr )
Give yourself time, and Open World solo experience to FAIL so you’ll learn what works, and what doesn’t.
Also be prepared to have abuse hurled at you. There’s a lot of narcissistic bad Hunters who’ve given the spec a bad rap.
For me personally, it’s been my favorite Class/Spec to play. I try others and have alts, but I always get bored and go back to BM Hunter. (I’ve got several.)