Yeah, you're right...ideally it should be done 7 days after ovulation (which in a 28-day cycle, with ovulation on day 14, would be on day 21). If you know when you ovulate, it's always better to have the test done 7 days after that than to do it on day 21.
Not that I'm aware. last month I did the CCCT & was tested 7DPO, just like on a natural cycle or on an injectable one.