My GPUs on my computer are getting older and cant really maintain a consistent framerate at 60fps for newer games at the higest. So I'm trying to lock down a 30fps with more visual quality instead of lowering the quality to get 60fps. I was watching my roommate play Far Cry 4 on his Xbox One and the framerate of that game, I believe, is 30fps. Even at 30fps, the game looks really smooth. But when I use Nvidia Inspector to limit my frames to 30fps and use Nvidia Adaptive Vsync Half Refresh Rate it looks unbeleiveably choppy on my PC.
 
Is there some type of effect or post processing effect consoles use to make 30fps look so smooth? And can you use that on a PC to get the same smooth effect?

I've been using RivaTuner to lock games to 30 fps. I've done so with several games on my previous GPU and the game motions are mostly cinematic. So is using Nvidia Inspector better? I plan to keep doing this with Metro 2033; I get low fps in that game with graphics settings maxed.

Reducing the FPS and limiting it is not going to improve the minimum FPS in games, and the minimum FPS is what usually disrupts the game fluidity anyway. If Vsync isn't enough to stop the screen tearing then ya need to lower the game settings or upgrade the GPU!
 
SLI can also cause stuttering and screen tearing just because of how it works. Split Frame Rendering SLI mode has each GPU render one-half of the frame, but it is notable for causing tearing because it's hard to balance the frame loads (sky vs ground in one frame, etc). Alternate Frame Rendering has each GPU work on a single frame but is notable for causing micro-suttering because syncing each GPU's individual frames isn't perfectly timed (synced) when the GPUs are struggling with the game load. You might just try gaming on a single GPU and seeing what that does for the tearing and stuttering, even if overall FPS takes a big hit.

Simply turning vsync on will raise input latency going to the display, but I don't think that will get what you're trying for? It can make things worse rather than better at lower frame rates.
 
I'm by no means a GPU guru (I read Tech Report / Anandtech for that stuff), but this article should interest you. It gets into the details between vsync, triple buffering, and the advantages/disadvantages of both. http://www.anandtech.com/show/2794/2 According to that you could try disabling vsync and enabling triple buffering. With a single struggling GPU it won't actually help because the GPU itself wasn't fast enough in the first place... but since you are running SLI it might smooth out the FPS delivery between the cards and the driver/display. 

One of the key problems is that games are built for the console and ported to the pc which usually means the pc has to work harder anyway.
 
Perhaps try toying with a few settings and see if you can find one that keeps it looking good and yet allows it to run better.
 
Plus it also looks like far cry on the xbox is not full 1080p
 
http://www.hardcoregamer.com/2014/11/21/far-cry-4-runs-at-1400x1080-on-xbox-one/118696/
 
Which would take some strain off the poor console ;)

Micro-stuttering is the terminology for that. http://en.wikipedia.org/wiki/Micro_stuttering
 
Tech Report is big on frame latency testing for that reason. http://techreport.com/news/21625/multi-gpu-micro-stuttering-captured-on-video Raw FPS alone doesn't guarantee smooth fluidity if the frames are unevenly shown on the screen or they're shown out of order. Or a monitor can show half of an old frame and half of a new one at the same time, which is what Vsync was supposed to fix. Here's Tech Report's latest "Inside the Second" article that goes into detail on the subject matter http://techreport.com/rev...ia-frame-capture-tools

I'm not familiar with NVIDIA Inspector or the Half-refresh thing you mentioned in your original post. You can create a custom profile for your monitor to a specific refresh rate and then turn on vsync, and that would effectively force your system to that FPS cap to achieve the same effect. 
 
I'm no expert which is why I provided all the links. What are you minimum FPS limits in single/SLI modes? The problem sounds like a single GPU isn't fast enough to provide stable framerates or sufficient minimum framerates to give you game smoothness. Yet when you SLI the overhead and inherent stuttering is still causing problems even though you have sufficient framerates. Verifying the min FPS in SLI would help. Consoles don't tend to have min FPS problems because game devs specifically optimize to the console hardware to fix them, PC users don't get that low-level of optimization. 
 
There's no perfect fix for SLI-related stuttering or jitter. It's an inherent problem with SLI and Crossfire, and why sites like Tech Report still recommend a single large GPU instead of two in SLI or Xfire.  As I hinted earlier you can try changing the SLI mode type between AFR and SFR to see if that helps at all. Enabling Triple buffering may help as well. But if the SLI setup is getting very low min FPS spikes then only a GPU upgrade can fix that.