Curious about structure of different competition classes? What are the ones you have attended like? What did you like dislike about it? 
We roll or do situational rolling (sweep/pass/submit) at a faster pace and with only short breaks between rounds. Often times we will get some competition intensity rounds in that start standing if there is enough mat space for everyone to have enough room 
I like the intensity and short breaks, and in particular starting from the feet. I don't have any particular complaints.
10 minutes stretching/warming up
5 1-minutes rounds grip fighting
45 minutes of competitive rounds (5 to 7 minutes per round, about 1-1.5 minutes break in between)
10 - 15 minutes of a Tabata workout to close it out
I like this layout, but certainly like the situation rolls too. Occasionally we'll do the pass, sweep, submit for 1 minute sprint rounds instead of the tabata workout.