You would need a full 2nd wideband setup to be able to see both banks if that's what you wanted.
Honestly, they're not great except for having a lightshow in the car and to be a big red flag if something goes badly wrong, but anytime I've had one, I spend more time stressing over it without there being an actual issue.
Having a gauge for tuning is handy, but usually they'll want one that can datalog, because they won't be watching the gauge as much as watching the log after the spin. They'll have an eye on it to make sure it's not going super lean or anything, but generally, it's a tool to build a tune, then it's just there for when things go south quickly.
I have a single O2 wideband for the Microsquirt, and no gauge in the car. It can be monitored on the laptop while being tuned and it will datalog a run so there's info to build off of. Having both banks would be more ideal, and I may toss a second one on when the blower goes on, just to make sure everything is happy, but again, there won't be a gauge lightshow in the car for my personal preferences.