There is a whole entire universe of back-stories there - not just Han Solo as a kid & young adult (but that too!), but Boba Fett, Lando Calrissian & Vuffi Raa, and like you know Darth Vader but there is also Prince Xixor the head of the Black Sun organization that was his top rival for power underneath the Emperor, and all manner of "minor" characters like IG-88 that almost took over the universe:-), oh and we should not forget Anzat the nostril vampires.

Robots, magic, love, intrigue, pirates, death, honestly like any story it's more about the strength of the author to tell it than anything but the universe is there to work within, and that's solid.

You already mentioned some of the top highlights: the Thrawn series - b/c Timothy Zahn is really good - and the rogue series, are both good. I found Michael Stackpole to be a bit distracting to read b/c of all the action terms, but if you can either know or ignore what "pitch" and "yaw" mean, they are great regardless:-). Especially Wedge becoming a pirate - fantastic!:-P

I am guessing that you only think you know about Luke/Leia/Han - e.g. Luke was this old hermit sage in the wilderness in the more recent movies - but at one point he was abandoned by his mentors and had to sort of just figure out the entire Jedi thing all on his own. He went from child/tween to young man to middle-aged long before he pulled back to his role of "retired sage on a mountaintop", which is the journey of a literal lifetime.

I think you are right to avoid the Yuuzhan Vong - not necessarily forever but at least to start with, b/c it was written in a time when all the other stories had already been told, and people were waiting on George Lucas to expand the universe to be able to tell more, so they are just strange, and also meant to be interpreted in the context of flat being "different" than any that came before. Ngl, there are some interesting stories embedded in that arc, but you can come to them later if you want - they are not good to start your jouney with imho.

Basically I am confirming your existing plan: read what you are interested in, those you mentioned are good, and once you read them, you may have a better feel for what you would be more interested in knowing next. e.g. I always thought the whole back-story of the Noghri was somewhat interesting, especially Leia's involvement, but until you read the Thrawn series you may not even know what those are.

I guess I should add that it will be really weird to be shifting universes all the time: the Empire (Thrawn and X-Wing series) is a very different place than the Old Republic, the latter is full of entitled people who barely know the meaning of the word "hardship" (and who all think that their lifestyle will go on & on forever) while the former rarely if ever mentions someone who has a stable source of income & a home, instead everything is slavery, death, and freedom fighting. So I confirm that your plan to read whole entire series at once is a good one, as those transitions especially between pre- and post-TOR will be jarring.

So get in there, and enjoy!:-)