kherigan, per another post "Better Late than Never" down the page, at least one cadet received a Campus Based 4 Yr. scholarship last week, in 8th Brigade (Boise St.). It is possible it was a last minute National High School 4 Yr. Scholarship, but the poster said it was Campus Based.
OP: 3 Yr. AD is a delayed scholarship that doesn't start until the beginning of sophomore year in college. The Freshman year gets zero Tuition, Fees, Book $, or Stipend from the Army. All those financial benefits starts at the beginning of Sophomore year when the 3 Yr. AD scholarship Awardee, who hasn't messed up during Freshman year (and thus has Validated), signs the Scholarship Cadet ROTC Contract, and becomes "contracted".
The 3 Yr. AD is more common than the 4 Yr. at Private schools last year and this year. I don't know which type is more common for low Cost (in-state Tuition) schools.
Room and Board is quite rare in Army ROTC. A few schools (let's say under 20) offer Room -or- Board, and probably less than 5 in the country offer Room and Board to scholarship cadets.