hmm... i've played on quite a few plastic reeds and they've all done perfectly fine for me.
my friend james purchased a legere studio cut plastic reed. geez... that thing was amazing! it played exactly, if not better, than the cane reed i was using at that moment... and i thought i had a really good reed. he used that thing during marching season. it still played well even at the end. very reliable reed.
and as for ligatures... as a whole they really dont do much except hold ur reed in place. i've seen many amazing sax players play on the regular old things u get out of the box with a new mouthpiece and still sound fine on it. however, i personally play on a bay ligature. it does feel quite a bit different from playing on a typical ligature. i've played on rovners, BG's and the vandoren optimum and this one beats them all out. you should, however, have good control of your tone before you try this ligature. it's also very, very sensitive. when u buy one (they're around 40 dollars) it comes with a warning label telling you not to tighten it too much cuz it would break. but yea, this thing really does wonders. i can definitely feel a difference from playing on the bay as opposed to the other ones.