I've got
Just Cause 3's performance finally in place here on my W7 64-bit, GTX 970, 16 GB RAM desktop PC.
To kill the nasty framerate drops + rises and any stuttering issues, here's what I did: I used NVIdia Inspector to set a profile specifically for JC3 to force both a 60FPS cap + also most importantly instituted NVidia's Fast Sync solution. Now, I'm around 60FPS most of the time.
Since VSync off or on wasn't solving anything here for me, so NVidia FastSync is somewhere between VSync Off and On, as it'll render only what it decides are the "good" frames (there's the Syncing) + flat-out discard any useless produced-frames (such as blank frames, anything it decides are "wrongly" produced frames, etc etc).
So, if you have an NVidia 900 series card or above: use NVidia Inspector to force a FPS cap of some kind (i.e 60 FPS) + most importantly use Fast Sync, if necessary. Seems to have took this to solve all my performance issues here.
Now, back to the game: causing chaos, doing nonsense, and blowing stuff up.
EDIT:
MysterD gonna MysterD.
But I do actually appreciate the information. It confirms that it's not just my subpar hardware, but that the game is actually poorly optimized. Also, it confirms that my decision not to buy was a good one, as I don't see the game getting a performance patch anytime soon that resolves all of these issues.
See, this is the problem w/ some modern PC games that are un-optimized: it can sometimes take a while just to get around these foolish & non-sense issues, just to get those issues thrown out. At least w/ Arkham Knight PC, I didn't have to resort to other crazy methods such as NVidia Inspector - as the options in Arkham Knight PC were in-game + internally there to solve my dilemma; I used the 30 FPS cap and performance problems were solved.
I went through this non-sense of an issue w/ both Homefront: The Revolution & now JC3, where there basically wasn't enough actual in-game graphics options around to actually solve my issue. Sometimes, even the official NVidia Control Panel doesn't solve everything, either - as they really don't have an option to force a FPS cap there, which is one thing JC3 really obviously needs. NVidia Inspector though can force a FPS cap, if you need to - which was key in stopping this from going bouncing b/t 60 frames to 80 frames w/ V-Sync Off.
NVidia FastSync can really get you much more frames with very little performance loss (compared to VSync On), when it actually works properly. You can get some of no-Syncing (b/c it doesn't have input lag) + benefits of Syncing (i.e. it tries to keep the good frames and chuck the bad ones).
I had to basically use NVidia Inspector to get at these issues + force things mostly at a driver level here, more or less - b/c I couldn't do so w/ in-game, couldn't do it w/ MSI Afterburner, or any other crazy way. Sometimes, this is the last resort - and sometimes, this actually works.