Portra 160/120, shot at 645, properly exposed and scanned at 2400 dpi with an Epson V600, can produce files with no visible grain. Now that Fuji has ditched all of its 120-color negative films except 400H, you can opt for a lower-speed film: this or Ektar. Ektrar is good too and has an even finer grain, but most of my work involves night exposures and portra is more forgiving - and it's easy enough to add saturation or contrast to a post.