Wheel bearing or tire noise? Subtopic tire recommendation please.

Hi,
I've been trying to diagnose a droning noise at about 70 km/hr on my
1990 Golf with manual trans. (In Imperial, 70 is about 35 mph). The
tires are Yokohama Avid Touring tires 175/70-13". The front pair are 2
years old, the rear pair are 8 years old. The sound is very much like
tread noise, a whirring that maxes out in volume at 70 km/hr. There is
a hunting to the drone (undulating) suggesting it's 2 or more tires
and the undulating is the droning being out of sync a bit between 2 or
more tires. I've swapped the 2 font tires, same noise.

To check for bearings, when I steer to the right right the noise
seems to diminish, so the right front bearing? Or just riding on
another part of the tire? Swerving left seems to increase the noise
level--so another clue to the right side front bearing or just riding
on different part of tire? I can't decide what it is. If it's a rear
bearing, steering shouldn't make any difference right? I've lifted the
car and spun the wheels by hand but no apparent bearing noise I can
hear or feel. And no loose wheels when the top of the tire is shaken
side to side.

Of the rear tires (Yokohama), I discovered one has a very slight
bulge on the tread so I'm going to replace the rear pair tomorrow. But
I don't think the bulge is causing the droning.

Subtopic:
The selection of 13" tires is very slim and I've narrowed down to 2
brands. What experience have people had with Toyo Extensa A/S tires?
They get good ratings and reviews (mostly). Next choice are Michelin
Harmony's (again mixed reviews, mostly good). My criteria are good
against hydroplaning, low rolling resistance, quiet ride, good tread
life, and responsive handling.

The reason I have 2 new and 2 old tires is a couple of years ago,
one Yokohama Avid tire had a separated belt so I got 2 new front tires
(match the tires on the same "axle"). I was going to replace the rear
pair the next year and guess what, I can't get Yokohama Avid tires
anymore. Should have bought 4 at the same time 2 yrs ago.

Other clues, I had Nokia Hakkapalita's on during the winter and the
droning noise was there too. So again I'm thinking bearings. Let's
see, what else? Oh tire pressure is 31.5 front 29 rear.

My next step is to take the 4 tires off my wife's '85 Golf and put
them on the 90 to see if I can eliminate the tires from the equation.
For stores, we've got Kaltire, OK tire, Fountain, Walmart, Canadian
Tire nearby.