Most every V6 engine that was designed as a V6 has a 60 degree arrangement. V8s are generally 90 degrees, and thus most 90 degree V6s are that way because they are sprung from the existing architecture from a V8. And thus, in order to be better balanced, they have to employ a single balance shaft with two weights to mimic those two missing pistons from the rotating assembly. If they do not, they are not as smooth.
The most commonly known (in this country anyway) of 90 degree V6s sprung from existing V8 designs were from Detroit. GM (Chevrolet, Buick, and Oldsmobile) did this, with the later Chevrolet (4.3L...sprung from the 5.7L V8) and Buick (3.8L sprung from the old early 1960s aluminum Buick V8.... the one they sold to Rover) V6s eventually getting the balance shaft. The Oldsmobile V6 was actually a diesel, of 4.3L displacement, sprung from their 5.7L diesel V8. Lots of folks don't even remember they built a V6 version, but they did. Usually stuffed sideways in an A-body Buick or Oldsmobile. All of GM's other V6s are 60 degree, although I am unsure about the old giant GMC V6.
Ford had taken the 5.0L Windsor family V8 and made first a 3.8L V6 and later a 4.2L V6, with the later transverse 3.8L applications and all 4.2L applications getting the balance shaft. All Ford's other V6s, the Duratec, Cyclone, Nano, Vulcan, are 60 degree.
Chrysler chopped two cylinders off their 5.2L V8, making the 3.9L V6 (which replaced the 3.7L "Slant" 6), but never did grace that engine with a balance shaft. Chrysler's "Powertech" engines, the 3.7L V6 and 4.7L V8, both 90 degree, are based on the same architecture. The 3.7L does get a balance shaft. The rest of Chrysler's V6s, including those sourced from Mitsubishi, are 60 degree.
Toyota's V6s, the original VZ series, the MZ series, and the still in use GR series, are all 60 degree. Nissans original VG series and the replacement VQ series and its derivative, the VR series, are also all 60 degree.
VAG's V6 is 90 degrees, and shares some design elements with their V8s, but their V6s do not have a balance shaft. They also have their VR engines, which are narrow angle, 15 or 10.5 degrees, and are really more closely laid out like an inline engine, with the cylinders squished and staggered together.
Honda has had both 90 and 60 degree V6s.
You can make a moderate displacement 90 degree V6s reasonably smooth if the crank throws are offset properly to make the power hits even. Honda probably did the best with that on their early V6s, but probably due to packaging eventually went to the narrower and more compact 60 degree layout they still use to this day.