Haha, no worries.
I'm far from a fixed income ETF expert. Although I've got a pretty good grasp on fixed income itself, I run a 100% equity portfolio and have for the entirety of my investing career.
So while I looked at stocks all day, I haven't looked at a fixed income ETF in... forever.
Right now, what I can tell you is that as these bond ETFs have bonds mature and new ones are added to the portfolio, yields will very likely drop. That is because new bonds issued are going to be at way lower interest rates.
This is NOT a good environment for fixed income investments right now. But, corporations are loving it because they can issue new fixed income at ridiculously low rates.
XHB is a solid one if you have a higher appetite for risk, and willing to take on more to get a higher yield. This is because it invests in companies with a BBB credit rating or less.
XBB is a rock solid, low risk bond fund. And, as you can see if you check it's recent holdings, the top 10 holdings are pretty much all municipal, government or provincial bonds.
Then there is ZAG, which is kind of like XBB except in the fact it introduces a lot more corporate bonds.
I'm curious, why were they suggesting avoiding ZAG? I mean, all fixed income looks pretty unattractive right now, not just ZAG.
If you're willing to stretch risk even further, could look to an emerging market bond ETF as well. Something like HEMB. Check out its top holdings to see what countries you'd be exposed to.
I hope this helped. Again, I just haven't stayed up to date on fixed income products. But, as always I try my best! Haha