Jerry,
Also, is there a difference in this during VFR and IFR?
Nope.
Obviously the profile depends on the overall weight of the plane (lighter plane can descend later)
This isn't true at all. Weight has nothing to do with the ability to descend. As Teroc explains, we tend to use "rules of thumb" that are based on a standard descent gradient (3 miles for every thousand feet), and from that a rate of descent required based on your speed (5xGroundspeed).
The caviat to this is on fast unpressurised aircraft, where a high rate of descent could be too uncomfortable for the passengers (ie, 5x200kts = 1000fpm). Pressurised aircraft has "cabin" descent rates not in excess of 300fpm - Big difference!