Everyone's experiences may be different, so I can only speak from mine personally; but I never had any "buzzing" issues with my '93 that had an approximately 5" (possibly lower) front drop with Western Chassis spindles & springs. The springs were actually trimmed just a bit because they sat more like a 4" drop. I ran a 225/70 up front with factory 15x7" mid-90's Caprice steel wheels. It had Doetsch-Tech shocks.
For the rear, I would definitely consider helper air bags if you plan to tow/haul. On the '93, I had a mini-notch that came with the drop kit. It had a flip kit with 2" drop shackle, so 8" total. I never hauled/towed anything, but it would bottom out on decent sized dips/bumps. It would've helped if I had trimmed the bed crossmember just above the "pumpkin." I ran a 255/60 rear tire on the same 15x7" Caprice steelies. Not sure if there are any differences between fleet & stepside bed pertaining to clearances.
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likaroc13, on Flickr
My '97 Tahoe has a 4" drop up front with spindles/springs. It has a 235/70 on 15x7" Wheel Vintiques smoothie wheels with custom 4.5" backspacing. Shocks are Belltech Street Performance. I've never had any "buzzing" issues with these either, & I've been over more rough roads in this than I ever took with my '93.
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likaroc13, on Flickr