I'm just curious, is it some sort of "special" TV? CRT? Plasma?
Do games even properly support 4:3 anymore? (I know you mentioned 1080p downsampling but again, curious
)
I would go with option A if you have to choose between the two. I wouldn't be too concerned about PC gaming on TV. Steam Big Picture Mode is great and you could always hook up a cheap Mouse/Keyboard AIO if you need a keyboard for chatting or whatever.
Just be aware that there is no Sony pixie dust magic available on PC that will do some upscaling shenanigans and you will not run the latest and greatest AAA games at native, real 4K30/60 with this setup. However, you will easily be able to revisit PS3/360 gen games or play indie games at these specs on your TV.
If you want to get a feel for what your specific combo can achieve in some games you are planning to play, you could always check for benchmark videos on YouTube. i3 6100/GTX1060 seems to be a popular midrange option.