Here's a link to netbookcheck's review of the Acer Predator G9-793 from November 2016:
http/www.notebookcheck.net/Acer-Predator-17-G9-793-Notebook-Review.173668.0.html
Heat generation remains an issue with intermittent spikes reaching 90+ degrees C (200+ degrees F). The G9 is a gaming rig and Acer makes little to no effort to reduce heat or noise. At 4.2 kg (9.2 lbs) it is effectively a desktop with a screen attached.
If you google teardown pictures of the G9 you'll see that Acer uses 2 fans located far away from each other to dissipate heat. In my opinion this design is preferable to either 1 large fan or 2 smaller fans right next to each other (Lenovo uses the latter design in the Legion). Acer's 2-fan spaced design should spread the heat over a larger area, but the reviewers at netbookcheck did register significant heat generation.
No matter how you look at it, this G9 is very powerful and very bulky - and Acer clearly decided there wouldn't be any point trying to hide that. If you already have a powerful desktop, and you're not an all-out gamer, the G9 is probably going to end up sitting in a corner most of the time. Alternatives that you can actually carry around include the Lenovo Legion mentioned earlier and Dell's Inspiron 15 5000 gaming line.
Cheers,
GreyCatz.