I do all of my training by time, but assume those distances will correlate to a specific time to you. And I do all training by power, as that takes all the variables out of the equation (wind and terrain and everything else regarding speed, heat and fatigue and hydration and glycogen regarding hr). I self-select cadence based on the moment and don't really ever pay attention to that, but I'm typically in the 95-105 range for shorter efforts, and maybe 85=95 on much longer climbs.

So with that said, it depends on what you're trying to improve/what you're working on. If I venture off to an area with proper mountains I might do everything at a pace just above what I could conceivably hold for an hour (FTP). Doing 3-4 x 20-25 minute efforts for a total of 80-100 minutes (a pretty huge workout as it'd be a trip to do a ride like that). Locally I do hill repeats for 5-6 minutes at a power that correlates to what I could do for ~10 minutes, and I'll work up to doing 20-25 minutes of that with 4 or so minutes in between (not equal recoveries). For very specific racing situations, I might do a workout where I hit a 3-3.5 min hill at 130% ftp, which would be about my 5 minute power. I'd try to do 4-5 of those, shooting for 15 minutes of very hard efforts, and I'd take an equal 3-3.5 minute recovery in between, maybe even 4-5 minute recoveries before the last effort.

For other very specific situations, I'll do 30s - 60s all out. 60 secs all-out is a workout I generally fail the first 2-3x I do it as it's as big a mental hurdle as a physical one. With those I'm taking 8-10 minutes recovery in between and trying to do 8-10x 30 secs or 5-6 x 60 secs. I like to do these when I'm already a little tired and don't want to do longer intervals. They hurt while you're doing them, but they're over and done quickly enough with a nice long recovery. Really useful if you have punchy rollers or selection points or even spots where a group picks it up for a sprint, etc.

Those are all structured workouts. I also do tempo or thresold workouts where I hit hills at a slightly harder pace, or I'll do easier rides and then ftp (1 hourish power) or higher on the hills to break it up, etc.

They're all different intensities, so it depends on what you're trying to improve. All of those efforts translate extremely well to the flats, too, though. Name of the game is varying how hard and how long you're on the gas, though. Builds a lot of specific cycling strength (delivering the power to the pedals) as well as aerobic fitness (delivering oxygen to the muscles delivering the power).