Gary as Kurt said the second tank would provide more volume to the system but it would not affect the CFM of the system (it will double the recovery time of the system however).

With good quality disconnects you should not see a CFM loss at connections however it could happen with poor quality ones and I have also seen it happen with cheap air hoses after the coupler.

Ideally you also will want drops (water traps) with drains below each coupler.

There is also some good information in this post.

inexpensive filter/dryer