Best way to connect a soundbar?

If your TV has a Coaxial s/pdif (Orange RCA Digital Audio)output, and the insignia sound bar has the input equivalent, then it would be worth hooking everything up into the TV and then into the Soundbar. Otherwise just use the optical s/pdif instead of the Coaxial. I personally prefer using the Coaxial. There is no difference in using the TV as a pass through because it's digital. Make life easier.

Use the Least Complex method.

Optical connections are generally the best choice,

and when they are the Only choice, just use them.

David is correct - the same 1's and 0's from whatever device is playing should reach the sound bar to produce identical sound.

Usually hooking to the TV is ideal. This allows your TV to act like a "Switch". When you change from PS4 to DirectTV with the TV remote, the sound automatically switches to follow the video.

If you plugged your soundbar into your DirectTV box - you could never get sound from your PS4 through the soundbar.

With an inexpensive Soundbar like the Insignia your probably not going to notice much difference, If you had a really Expensive Focal sound bar or something by Bowers and Wilkins then maybe there would be a slight difference with a more direct connection....A lot has to do with the quality of the optical output from your TV. An older plasma probably does not put out as good a signal as a modern 4K UHDTV does...but then what are the drivers inside of the Insignia capable of Most of the improvement if any would be in the upper frequencies so if your sound bar does not have tweeters or is even capable of playing anything higher than 15 KHz then any gain would be lost in translation....also tighter bass might be possible from a higher bit rate transition, but if the drivers and the amp can't do it then there is no noticeable difference to ones ear....

That depends on whether or not your TV has a built in equalizer function that you can adjust and the same goes for the soundbar. You may find that running it through the TV first changes the sound. Play around with your equipment because the best way to connect any kind of audio equipment is the way that sounds best to the person listening to it.