SegWit transaction preference

[d4n13]

Could anyone ELI5 how SegWit transactions factor into SegWit blocks?  I get how SegWit blocks segregate the witness data and how that is advantageous because it increase block size for the client and increases transaction count (and likely reward) for the miners, but how does all this tie into SegWit addresses?

• Do all outputs of a transaction need to have segwit outputs for them to have their witness data segregated?
  
• Do all inputs and outputs of a transaction need to have SegWit adresses for them to have their witness data segregated?
  
• Can a transaction with mixed with some SegWit inputs and some SegWit outputs have their witness data segregated?
  
• Is it believed that, statistically, this profiling by miners will cause SegWit capable transactions to cost less satoshi/byte than non SegWit transactions?
  

Thx

[aleksej996]

1. As far as I understand, no.
2. No, it is just inputs that are treated differently. I think.
3. I assume that it could, at least for those segwit inputs. The non-segwit inputs will have to be on the block in entirety.
4. It is not believed, it is understood. Segwit transactions take less space on the block then the non-segwit ones as they don't put a signature on the blockchain.
Less space that transaction takes means that miners take up less of the space of their block by including that transaction then the bigger ones, which means they can fit more of them in a block for the same price. With power of supply and demand prices go down for segwit transactions, as they are less costly to include.