Yes, road buzz is a very individual thing. Someone should do some research on it, they could make a gazillion bucks if they figured it out.

Yes, width of tires (and psi) has a lot of effect on road buzz. Mind you, my aluminum bike had 37 mm/75 psi tires and I still felt the buzz; while one of my steel bikes has 23 mm/110 psi tires and gives me no buzz at all. (other than the buzz of bicycling joy!)

Wider tires do not necessarily require wider rims. Your best bet is to take the bike to the LBS and ask them the maximum width low-pressure tire you can put on your bike. That will at least give you a starting point to think from.