Here's a couple more ideas for you to check out. Maybe it's just a combination of stuff?

1 - Inner driver, or inner CV joint on axle. The tripod bearing wears a low spot in the track where it rides, so now the axle can wobble a little off-center. Usually causes more vibration on the throttle vs. coasting. (But this doesn't explain the vibration while braking.) Get under, grab the axle, try to shake it (make sure the car is properly supported...) The inner joint shouldn't be loose.

2 - Other ball joints, like you said you're gonna check the lowers. Also check the little balljoints on the steering tie rods. Check BOTH SIDES. It feels like one side, but that can be deceiving.

3 - Brake rotor. Uneven imprinting of pad material onto rotor; get them resurfaced. But usually this vibrates at moderate braking as well as hard braking?

4 - Swapping tires around is a good idea. Definitely check that out.