What you're asking would probably take three pages of posts to explain but I'll address a few points.
#1, you can compare the two links below and see the differences in signals.
http://www.nba.com/analysis/00422964.html
http://www.nfhs.org/staticcontent/pdfs/bbsignals03.pdf
The differences in floor position are less and less each year. Most of the technics used in three man officiating was developed by the NBA and trickled down to the NCAA and NFHS.
The rotations/switches are somewhat different but nearly as much as they use to be.
#2, Officiating Philosophy
Just because contact occurs, it doesn't mean there's a foul. In the situation that you described from the announcer and Ronnie Nunn, the myth is "reachin' in." There's no such thing as reachin' in. If a foul occurs, it's either illegal use of hands or holding. But it's not a foul just to reach for the ball. In the situation described, why penalize the offensive player, who has a clear path to the basket, just because the defender stuck his arm out? Unless the contact places the offensive player at a disadvantage, then a foul hasn't occurred.
That's what Ronnie was saying. Good officials apply the principle of advantage/disadvantage to such situations. If an advantage is gained or a player is placed at a disadavantage because of contact, then a foul has occurred. And that's true at all levels of play.
NBA officials are going to ignore the trivial stuff, like the extra step on a drive to the basket, or bump that Yao and Shaq exchange while banging in the post.
#3, the big difference in the game is the strength, quickness, and speed of the players. More contact is allowed. When you have 10 such players moving together in such a small area, the game is going to be physical.
#4, a few rule differences:
There is no closely guarded situation in the NBA. An offensive player who has his back to the basket and dribbling the defender down into the post has less than 5 seconds to make his move. This is designed to cut down on "isolation" plays and involve the team more.
The NBA has things like away-from-the-play fouls, elbow fouls, punching fouls, and loose ball fouls. The NCAA doesn't.
The NBA also has a defensive 3 seconds rule, which replaced the illegal defense rules from a few years ago. There are no such restrictions on the defense in the NCAA.
You can check out the rules for each at the links below.
http://www.ncaa.org/library/rules/20...ball_rules.pdf
http://www.nba.com/analysis/rules_index.html
There are other officials here who have actaully officiated within the NBA rules. Hopefully, they'll pop in and tell us more.