No matter how you hook them up, the pack (series or parallel) remains as 20C, the same as the individual cell.
In series you have a 2s100mAHr, which can supply 2A (20 C) total out.
If you put them in parallel, you have a 1s2p200mAHr pack. Each cell still can supply 2A, but in parallel it is summed to 4A total. But since the capacity is doubled to 200mAHr, so the net C is still 20C.