The depth chart is the list you select regarding who is a substitution/reserve in which position etc.
If you have "coach decides" then he won't put very much emphasis on who you want to substitute for which position and will instead use mostly his own initiative.
In contrast the alternatives just decide how much he listens to your choice of depth chart basically, so strictly from depth chart means he wont take someone you want to sub in at SG and play him at SF for example.
Hope that wasn't too confusing :)