It really depends on the race and the kids who are racing. For example, there was a whole team of suuuper strong juniors at the crit today, but they didn't do the juniors race, just the cat 3. So, the juniors race was a lot calmer than the 4 crit. I never raced 5s (long story) so I can't speak to how they compare. The biggest thing with juniors is that there seems to be greater variability in the field. You have kids who are cat 1/2, racing junior nationals, etc. And you also have kids like us who are kind of new to racing and just getting used to it. When you race a category race (5, 4, etc.), most everyone in the race is at about the same fitness level, so it is more predictable.

The only advice I can give is to do a crit where you can do both your cat race (5) and also juniors. If you have decent fitness, doing two 45' crits in one day isn't too bad. But you should check because at some races (btkill, for example), you have to be a 4 to do the juniors race. But I think the crit I was at today was all cats for the juniors.

Just get out and race man and stop worrying about it

It is a blast.