Generally speaking, crappie are not line shy. While braid is definitely visible to fish, its small diameters tend to make it less intrusive. You will also be using a leader of at least 4 feet. Mono or fluoro is difficult for crappie to see and therefore unlikely to spook them. However, In heavily fished areas, fish of all species can be a little line shy and easily spooked. If this is the case, you might be better placed to fish fluoro in these locations. By and large, braid shouldn’t present any issues. Be aware that heavily fished areas where there’s very clear water and little wind are always best fished with mono or fluoro.