I’m not sure any version of TOS is airing on U.S. tv right now. I know TNG was running the SD versions of TNG last year when the channel was briefly unscrambled on my system. Maybe something will happen for the 50th anniversary? CBS seems to think streaming is where the money is now though.
I think the original two episode DVD’s look pretty darn good upconverted. But I grew up watching well worn syndication prints on tv. 😉