I'm a Lumia 830 owner here.
First off, I'm not sure why you'd want to downgrade from a 950, which obviously you've had the money to buy it in the first place. You said that the phone does not justify the price, so is this a good enough reason to return the 950? Or is there something else that affects your decision-making?
Also, if you want to downgrade, I'd suggest you to go for the 640XL. It is definitely MUCH BETTER than the 830 in terms of camera and screen size, although the pixel density is quite a downgrade (both 830 and 640XL have the same resolution, but since the 640XL has a larger screen, thus it has reduced PPI). Here's a quick pros between the two phones:
L830
Pros:
1) Camera has OIS, along with dedicated shutter button [Pureview Camera].
2) Wireless charging
3) Hardware button
4) Better screen (higher PPI)
5) Better design (down to personal preference)
L640XL
1) Larger screen
2) Main camera and FF-Camera has better MP than the 830 [13MP+5MP vs 10MP+1MP]
3) BETTER BATTERY LIFE (This here is gold!)
4) Cheaper (Depends on your country. Here in Malaysia, the 640XL is cheaper)
Also, the reason why I suggest the XL instead of the 640 is because the 640XL has a matte back plate, which is much better looking/feeling. The glossy backs aren't really good as wear and tear effects is more obvious on them compared to matte back covers.
I guess that's about the only difference between the 640XL and the 830.
But if you want to downgrade, and have a bit of money to spare, I'd suggest you to look at the Lumia 930 or the HTC M8. Should still be a good phone, and it won't be too much of a step-down in terms of hardware-performance from a 950.
P/S: I'm running the current version of W10M on 830, and it runs smoothly. Only a few minor bugs here and there, but I believe MSFT will iron those out soon. They always do.
PP/S: Also, check out NuAns Neo. That phone is from Japan, and supports Continuum! Look it up!