I believe the answer is yes to both. Any plant that self-seeds should do fine being planted in late summer/early fall. My brown eyed Susans self-seed rather prolifically, and the new plants are just starting to grow. Additionally, I originally planted them in the spring (a combination of planting starts, and broadcasting seed directly) and I had lots of blooms the first year. So I think you’ll probably be fine either way.

if I started them now, how long would I have to keep them cold? I put the seeds in a paper bag and put them in the fridge on sat. sept. 22.