The SJG version of HQ was much more traditional in presentation, the HQ:G version takes the story beats ideas from Robin Laws and integrates them in. The version of HQ standalone on the Chaosium site is the same (as this is HQ2). I suspect that you could ignore the story beats element if you wanted to.
I've only skimmed the rules in HQ:G but what I can say is that all the versions post the original box set have been much more clearly presented than the Hero Wars box set ever was and that you could still draw on HW books.
If I was to revisit Glorantha, it would be via HQ, or via HQ ported into Wordplay/Tripod.
Sorry afraid I was in 'deep freeze' when Hero Wars came out, so I can only talk to HQ:G, which is fairly easy to understand with few errors. That said it is quite a mental shift to go to 'conflict resolution' from the task resolution of most trad RPGs.
I like both RQ:G and HQ:G, the former is good for crunchy tactical combat, the latter for fast-paced more narrative styles.
About the HQ:G rulebook, it's a nice all in one Rules + Glorantha. I'm currently on a break from Glorantha, having run many, many games/con games over the last 30 years, but at the moment it's the ruleset I'd probably use to run a quick campaign.
I've not used it in anger, but it's the first of the HeroWars/HeroQuest books that I would have been 100% happy passing over the table to my players.
Apparently, some of the worked examples aren't 100%, but that's not surprising because they were hurriedly thrown together before the authors went to Eternal Con
Free League just shared a vid of unfolding the proof copy of the cloth Shire map for the One Ring kickstarter, and I guess now I'm resisting that. (Or more likely the Eriador one.)
(Edit: Mind you, it's about £35 as an add-on and I'm watching pennies, so my resistance may be sadly successful.)
Then Marie Kondo's wisdom kicks in, with strong warnings of Tsundoku.
So depending on the game engine, I get a boon to Resistance vs Temptation. Unless it uses something I already play like my many Third Party 5e books, or my YZE hoard of Fria Ligan or the Modiphius 2d20 (Homeland Revelations this fall). Yes, yes, and Savage Worlds too.