My league does LB/DL/DB

I have both Derwin James and Cooper Dejean. Who do I start, and should I drop one and risk someone picking up or have one sit on bench the whole season?

your going to start derwin james every game over dejean. dejean isnt even considered draftable unless you have some odd scoring.
DB is essentially safety, not many cbs are worth rostering/starting

Safeties will have more tackles/sacks/tfl than corners so they should generally score more fantasy points.

tyty, dropped dejean and picked up Brian Robinson Jr