I assume you mean frameCount (instead of framerate). It is quite accurate with regard to frames, but indeed not time-based. Never use delay, because it stops the flow of the program. There are many, many threads on timers so a suggestion is to search the forum for all the previous timer-questions. But to get a general feel of what is possible with regard to millis() with regard to a timer see Tip 15 of my 25 tips blog post.

" is there a way to make milllis() start on command?"
This is becoming a FAQ... I wonder if I should make a new entry in the Technical FAQ, or if I just need to address the question in the existing How do I display a message for a few seconds? article.