I recently discovered split address on www.bitaddress.org, but I am not sure what this actually should be.

Basically you have one public adress and can choose how much "shares" (I assume those are priv keys, they look like it) are generated and how much of those are required to send from the address.

BUT, the public address is f.e. 14DMsSty9S6M51Bxh3X2ZiFhRvdfNhXAjV, why is that? I thought multisig adressess always start with a 3? Is the 3 at the beginning only optional?