Good questions. I wouldn't personally upgrade for BT alone, but the last time I looked into it BT audio was still questionable. I have not looked at the spec for quite awhile so I can't say performance wise yes or no. It may have matured into something good. I do know it's very convenient.(I have headsets and a BT speaker).
Can't remember if it displays song info and stuff. It very well could, but I only use AirPlay to my airport express. That way I have all the album/song info/volume/track control with me on my phone wherever I go. I'm sure there are other devices that do the same thing, but I don't know what they are. Not an apple fanboi but it works so damn good. I wouldn't upgrade for BT alone, but their are reasons I would, like built in AirPlay, streaming apps, connectivity, and hdmi just makes it easy. And don't forget atmos. Or maybe I shouldn't have said that...lol
Did you mean adapter from the phones headphone jack? This is what that would look like.
RCA Cable, iXCC 6ft Dual Shielded Gold-Plated 3.5mm Male to 2RCA Male Stereo Audio Y Cable
https://www.amazon.com/dp/B019D048XC/ref=cm_sw_r_cp_api_xRNgzbEZSZV8F