We'd think this depends a lot on the type and theme of RPs. We've often found that on average (but with exceptions) the age of the RPers is relative to the section they post in. (younger in free, older in advanced). Themes that are of more common interest to those who are younger, will by that logic be more often seen in low-casual/free RPs.

Still, we'd agree with some of the above. The standards aren't different. There's just overpopulation in casual and lower populations in the others.

Of the three RPs we're in, one is (high-)advanced, one is technically casual (but consistently has advanced-length posts) and the third is casual with leanings towards longer posts (but not as long as the second). So you'll easily be able to find RPs with more than high enough post lengths for ya in casual.