Hi Marco;
1) PB 12.6's 64 bit support is only applicable to native P-Code compiled EXE's (not Machine [M-Code]).
2) Web services are still only 32 bit (as Bruce points out). You still deploy them directly to IIs from the IDE or via an MSI built from the WS project.
3) The WS's Application Pool must still be registered as 32bit & running in "Classic" mode.
4) The Winform compile option is till only 32 bit.
Hopefully, we will hear a lot more about the PB road-map at the 2015 PB Conference when Sr VP Dirk Boessmann addresses the conference attendees on Friday AM on PB's future. Friday May 8, 2015 | NCPBUG
Regards ... Chris