I believe most folks don't give drag much serious consideration when crappie fishing. I pay a little attention to it when I first start my season, by pulling from the reel by hand. After 60 years of fishing and having made mistakes along the way, I've learned what is appropriate for the species I'm targeting. I think this method is both adequate and correct, under most circumstances. Trial & error will certainly convince you as to what you need in short order. I've never used a scale to set a drag.
The other option is backreeling, which, we did quite a bit in decades gone by. Very reliable and efficient way to fight big fish. Not so sure it would work well with crappie however. We used backreeling because of the simple, more often inadequate, drags that were available to us back in those days. Technology has come a long way and competitiveness among manufacturers require a decent reel to have a decent drag. Besides, I enjoy listening to the "whirrr" of a drag!
"A voyage in search of knowledge need never abandon the spirit of adventure."