I have used AP and am working without EAD for same company

You can extend your H1B even you have used AP. I am not sure about transfer because I cannot find anything about transfer in the memo. However, I have teammate who had used AP, and was laid off, and found a new job, the new company was going to file transfer for him even knew he had used AP. But just before the company did the transfer for him, his GC was approved. What a lucky guy, but I don't have a solid evidence that you can transfer H1b after using AP.

Hope this help.