i am not an expert but this is my experience,
Yellow tang or bristle tooth should be okay for yoy, I have a 2tank and have had a YT in there for 6 months now. Normal behavior. I threw a bristle tooth in and the Yt and him never fought , only lasted a month though because the bristle tooth kept pacing the glass and I figured he would be better off in a bigger tank.
I wouldn’t recommend 2 tangs in a tank below 4ft. also Purple tang is too aggressive
For tangs it just depends, on the environment ( what fish is in there, rock scape, how often do you feed, water quality , also not every yellow or bristle tooth is the same. So I agree with above post , you need to observe
Everyone recommended a bristletooth instead of the YT and the bristle didn’t work for me.
in the end, although I’m sure I could get another year or 2 out of the cube with the tang .. I am planning a 5ft peninsula by next year.