W:hat's a playable FPS?

Solution

If I had to pick between evenly spaced 10fps or 15fps with high jitter, I'd probably pick 10fps.

Frame time variance (jitter, which may also be perceived as stutter) is much more annoying than uniform low FPS.
Personally i play on a custom gaming PC and require 60 fps to find a game playable but someone i play online with in a game called ark uses a mac book air and averages 10 fps and some how still manages to keep up and game. It's all on what you can get used to i guess
 

If I had to pick between evenly spaced 10fps or 15fps with high jitter, I'd probably pick 10fps.

Frame time variance (jitter, which may also be perceived as stutter) is much more annoying than uniform low FPS.
 
Solution
Correct, and its a problem often overlooked or people dont know about it.

Basically what has happend is that FreeSync and GSync exist as a solution to a problem that shouldn't exist in the first place. Game developers aren't given enough time to optimize the games, are too lazy, or GPU drivers are involved as well.

A console game at 30 FPS optimized would run smoother than an unoptimized game at 60 FPS.