There's far more "tweaking" going on on the PGA Tour than the ATP, all the way through the bag. For proof, spectate at any event and take note of the large trailers on site with tour techs inside dialing in the equipment for all the competing players.
On drivers, fairway woods and hybrids they mostly tweak with shafts and lead tape to change swingweight, launch angle preferred ball flight (does the course have dog lefts? Help me draw!).
Irons get tweaked for lie and loft with tape and/or bending the heads. Again, course conditions have a big influence on the adjustments (heavier rough...perimeter weight gets added for more stability). Wedges may get tweaked or substituted with different bounce specs because of the greens areas and bunker conditions.
Putters, too...slower conditions on the greens will lead to heavier set-ups.
I applaud the work the top techs for ATP players provide but it's not nearly as intensive as what the PGA tour techs are called on for every week.
"When a man is tired of London, he is tired of life"...Samuel Johnson 1777
"When a man is tired of Federer, he is tired of tennis"...stringertom 2014