I am hearing a growl or steady hum noise?

I'm hearing a growl or steady hum noise as I'm driving, and it gets a tad louder when going faster. If I slow down fast, it lowers or lessens. It doesn't do it at park. Going 50 MPH it is not as loud. I don't notice a difference on turning but going thru drive thru I hear a little tiny pop or going over hum on road at timed. I'm going to change the 2 front hubs though not a lot of play on tire test. What else should I look at?

I hear a rundown noise as I slow down fast from 45 to 30 mph so I'm not sure if it's differential or u joints or transmission. A tad of play in rear bearing too but not much.

Also, at times I'm getting a catalytic code p0420 insufficient. So, I'm not sure this factors it.02 tests show a few saying low on them an 1 says high. The cat tests say normal on some an high on one. Not sure if that's a indication or just what it's measuring but the temperature or use. Sometimes it seems a bit sluggish on acceleration.

Any information is appreciated.
At times