Oh, haha, I'll answer them to the best of my ability ✌
A single/super sim is basically one sim that achieves "everything" really, like maxing out skills, careers, etc. Since the jobs split into two branches, my personal super sim does one branch while his clone basically does the other so I could have both lol
I think it depends on the pet's traits, really. My one jumpy dog wakes up for every little thing, but most of the households I play with pets generally have them sleeping around the same time, occasionally waking earlier to do their business or play with something. I have one cat that loved to wake up early to go into the bathroom and stare at the toilet (it was his favorite thing)
The only issue I had with C&D was having puppies/kittens, since they can't use stairs and many of my sims couldn't get the memo of picking up the tiny thing to place them somewhere else lol
It's pretty so-so, really. With children and nothing else to supplement their gameplay, it gets boring fast. They only have 4 aspirations, and take twice the amount of time to skill up for adult skills (dependent on the skill anyway, since some skills like photography don't need you to max creativity first). It gets repetitive and kind of draining. At least with Parenthood, it feels like you're doing something else than getting them to wake up, do homework, go to school and come back annoyed, rinse and repeat lol
School projects are fun, and as a ridiculous sim parent, I hoard all of my kids' school projects. Teenage mood swings and phases give both kids and teenagers something more to differentiate themselves from young adults aside from building character values.
I recommended Kids Room since it introduces Voidcritters, a pseudo-pokemon like card game where children can collect said characters with two versions of each card. They can battle them and trade them with others, plus the furniture and CAS options give them more of a pre-teen feel; So if you're the kind that likes to sort of dress the kids as they 'age,' Kids room is pretty great. I added in the Toddlers stuff pack as well since base game toddlers are definitely lacking in so many things. They have absolutely nothing lmao. That stuff pack has a toddler jungle gym as well as the laughable ball pit they can play in, so it gives them something to do really--As well as clothing options, of course.
GF and Seasons add a couple of extracurricular activities, those two being Scouting and Drama Club respectively, so picking those up without parenthood should give you some more gameplay with the younger stages if you wait on Parenthood. :)
By that, I mean the whole environment changes, like the sky and lighting, in Strangerville's case the more you delve into the mystery. You enter the unusual town with it appearing like a more orangey Oasis Springs, but as you discover more, the skies begin to dim and well, several townies begin doing weird, creepy things. It's rather nice--I'd say more but I'd ruin the mystery. One of my favorites for sure.
Island Living has an active volcano that only ever does anything when you do the conservatory career to progress it. Jungle Adventure doesn't actually affect the area, but it has several RNG outcomes to which temple you'll end up in, so it's kinda good if you want to burn time snagging treasures. (Also it's great if you're extremely broke, since authenticating artifacts really rakes in the dough)
I never got to play TSO, my first game was TS2--But if I compare it to TS3's fame system, I do like TS4's rendition of it better. The paparazzi can't see me in my high rise doing terrible things the way TS3's insane ones do, so I get some privacy LOL
As you climb the road to fame, you can get perks and quirks that change the way your famous sim functions. Some notable quirks I love include Stans, which are basically stalkers, and Vain Street, which makes your sim want to check themselves out in the mirror every so often.
If I compare it with what I can read on Superstar, you only get access to the Acting career in GF. Karaoke is introduced in TS4 via City Living, the Photography sets are in both GTW and expanded on in the Moschino SP, and the spa items are in Spa Day.