Is there a reciprocity or compact agreement between Pa. and Tx.. concerning traffic warrants?

Answer 1

Article IV, section 1 of US constitution provides that:
"Full Faith and Credit shall be given in each State to the public Acts, Records, and judicial Proceedings of every other State."[1]
So Pa pretty much has to honor TX traffic warrants, IF PA decides to prosecute the offender who now lives in TX(which they won't)

Answer 2

That is really going to depend on what the warrant is for and what class it is. Most of the minor classes of warrants will only be extraditable out of the state that it was issued in. Some of the major ones will be extraditable from surrounding states only and the felonies are usually extraditable nationwide.