I can answer to this question… the answer is NO.
The only available patch to a Plextor firmware is a RPC1 version made by The Dangerous Brothers.
The drives currently supported are:
PX-116A (rebadged Pioneer DVD-120)
PX-116A2 (rebadged Pioneer DVD-121)
You can find them on TDB’s homepage. Of course, be warned that flashing such a firmware voids your warranty
(but I have a feeling that you already know that ).
About media, other people here are much more expert than me, so they will tell you.
However, a general rule (for the current Plextor drives, we’ll see for the new 716) is:
if you feed Plextor units with good media, you (generally) get very good results.
Some folks here show 12x burns made with the 712A that are really outstanding .
If you tend to use cheaper media, probably the NEC is a more appropriate choice
(at least, it was true for the 2500A that I have just sold out,
waiting for the 3500A I have ordered some days ago ).