Try giving Casual a go, and look for RPs that have a "no speed posting" rule. That usually means there's a loose turn order and it will stop that scenario from happening again. There's really not that much more requirements, if you can write a small paragraph or two you're totally fine.

I had to leave the RP section on my first forum years ago because it went from what's Casual standards here to speed posting Free. I couldn't keep up with like 100 plus posts a night, I didn't have time or interest in doing so. 

The worst part is, usually a night's worth of speed posting ends up moving the plot along less than a decent Advanced collab and have barely any of the details that make it interesting to read while being way more time demanding.