terminator5105

really appreciate the help and the problem is solved, i disabled the 750ti from the device manager and exported only with the 1660 and then voila a beautiful export 
 

other Than that there really isn't any advantage to buy it 
 

Maybe the update need more ram to perform.
When ram is depleted, the rest will use your ssd space, that's when you will see stutter.
Check the temp while playing games and also ram usage on the task manager.
As i said 8 gb is pretty tight. 

Depends on the game, settings, resolution, refresh rate, the weather.
 
That being said, a 9400F will keep up with a 1660 no problem in the vast majority of cases, or even with faster GPUs than that.
So you're fine.

no

it was in another topic that i talked about before 

If you have the 1660, using the 750ti is redundant and maybe problematic.
The 1660 probably has 3 or more port.
Anyway 80c is perfectly fine, although the ideal temp is under 75c.
You can tweak the fan curve to a higher rpm.

Sounds like a very busy graphics card...

I never said they were bad... I said they were good. I have a 1660Ti in my laptop and it shreds 1080p 144fps in lots of games. I just said it's a cheaper, better option than a 5700xt, etc for 1080p

Yup. As you can see it's basically useless by now. Other than to use it as a display adapter in another PC it's pointless keeping it. 

Which is why I didn't mention it. Vulkan could theoretically also use multiple GPUs, but since there are no games using such an option, it remains only a theoretical option.

Display adapter. 
 
Or sell it while people somehow still choose the gtx 750ti as the go-to ultra low budget used machines. 
 
Even tho there are usually better paths to go down

^^^. DX12 mGPU would technically work with any cards, but I don't know that any game dev has actually implemented that part of that specific feature in any game. That + most games do AFR anyways - Alternate Frame Rendering - where it renders frames in a 1-2-1-2-1-2-1-2 pattern, alternating GPUs. So even if you could pair two cards regardless of SLI support, your setup is only as fast as the slowest card, meaning you may as well use two 750 Tis since that'd be more useful. 

In this case it would likely be a performance decrease. With the addition of some stuttering. 
 
Just use it as an extra display adapter if you need it.