Some FFPs do allow restrictive double dipping like SQ's PPS. Haven't heard of any that allow you to earn base miles in one account and bonus miles in the other!
Does FR still give out freebies? I haven't got or heard of this for quite some time now. I did enjoy the 2x bonus a couple of times.
Generally in the last few years they've been quite fast in crediting miles. An SMS when you land after flying AI is always nice to receive when you turn on your phone. And T+1 days after flying *A partners has been the norm for me.