Before transmitting the varibable datas they will prepared with a SAPScript layout set, means SAP will not be disburden in an effective way. Using an extern product when printing complex documents the printing can be faster in relation to common SAP printing. By the way, there are a solutions for multi documents sets on laser printers, but later more. All relevant printer languages are supported, but in relation to PCL only the rudimentary basis commands. Depending to the used software nearly all printing systems are supported under MS Windows, but in some cases with really big data streams.
Every bigger investment requires continuity.
Depends on take over of the datas. Printing preparing had not be changed in version 4.0, only form creation is supported with a MS Windows SAPScript generator, but at least this generator generates SAPScript layout sets and nothing had changed in relation to functionality of SAPScript. Of course this confrontation can not offer you the all over including solution. You should have a look at this solutions, because you will find solutions for laser printers you would not normally think of. We have the possibility to create forms as you want them to be, only by using the standart tools of SAP and in some cases a flash memory solution.