You're probably going get 100 different answers... Everyone has different tastes on leader length, leader poundage, spoons, spoon color, etc...

I use 20# year around with spoons. I feel spoon movement is more important from the spoon itself than movement from the flasher. After all, they are tested this way prior to marketing... However, I also use the flasher to make the spoon "stop" (definitely a crippling action) by applying certain bends to the spoon.. A lighter leader is going to apply better action... If you choose to go with a heavier leader, make sure you use a uni-knot (or something that makes a loop) to free the movement...

Small flashers work well when both large and smaller fish are together in an area.. The main reason they were built was not to reduce drag (this is secondary), but rather on the theory of small fish-big fish competing for forage...

My spoon preferences depend on the season, size of bait, size of fish...

Devils Tail
Diamond King
Fishlander
Northern King (Great Sand Lance profile)
Coho Killer
Coyote

Half the fun is experimenting...