You don't need PlexTools to change settings of your drive because by default the most important things are enabled (like PoweRec, BURN-Proof, AutoStrategy). But, that said, I do advise you to install PlexTools because it let's you enable things that are not enabled by default. For instance, SpeedRead DVD is disabled by default and when you only use your drive to rip DVD discs with, it's nice that is reads at full speed instead of being limited to 2x (default). Booktype is also disabled by default. This means that the drive doesn't "turn" DVD+R and DVD+R DL discs into DVD-ROM discs. I always have these settings enabled because generally speaking, DVD+R discs with their booktype set to DVD-ROM are more compatible with standalone DVD players.
Last but not least, PlexTools has a lot more interesting features that work great with your Plextor drive. One of these is the PI/PO tests to measure the disc quality of your burning DVDR/RW media, C1/C2 tests to do the same for CDR/RW media, DAE support, PoweRec, GigaRec, SecuRec, VaiRec settings, etc, etc.