Performance of Difference Table Functions

We have some views in which CONTRACT_YEAR is harded coded (otherwise filter on CONTRACT_YEAR would not be pushed through because of the complexity of view definition). Now we want the CONTRACT_YEAR to be flexible, so want to replace these views wiht table functions. We are exploring pipelined table functions and regular (non-pipelined) table functions. We saw very different performance of them. Could you advise:

1. Why one is better than the other?

2. Any better solutions than what I have here?

Thank you in advance.

All the four functions do exactly the same thing, but in idfferent ways. The code is simplied.