What you see is what you get
At this time we are not accepting any additional races than what you will find in our lore. The races available CAN produce offspring but not all pairings can.
Dragons are not capable of reproducing with other races than their own.
Mixed sub-races generally inherit appearance evenly from the parents and the magic swings one way or the other.
It is possible for members of two different races (other than dragons) to reproduce though the success rates are substantially decreased. They inherit appearance and magic much the same as most other mixed races. It is also very common for offspring to be infertile.